1
00:00:00,000 --> 00:00:05,040

2
00:00:05,040 --> 00:00:08,440
>> SAM LEVATICH: Welcome to
section for this week.

3
00:00:08,440 --> 00:00:10,040
I am not Andi.

4
00:00:10,040 --> 00:00:14,590
Andi has fallen sick this day, and I
have been sort of called in last minute

5
00:00:14,590 --> 00:00:15,700
to take over.

6
00:00:15,700 --> 00:00:20,920
It's flu season, so make sure that you
are staying clean, washing your hands,

7
00:00:20,920 --> 00:00:24,800
and eating healthy so that
you, too, are not bedridden.

8
00:00:24,800 --> 00:00:26,870
>> But without further
ado, let's get started.

9
00:00:26,870 --> 00:00:29,970
Today, we're going to talk
about PHP a little bit-- how

10
00:00:29,970 --> 00:00:33,900
PHP relates to HTML, how it
relates to CSS, and some of the web

11
00:00:33,900 --> 00:00:36,100
stuff you did on the last assignment.

12
00:00:36,100 --> 00:00:37,930
We're going to talk a
little bit about SQL

13
00:00:37,930 --> 00:00:41,360
and how you can work with databases,
which is a pretty key component of P

14
00:00:41,360 --> 00:00:43,650
set 8-- P set 7.

15
00:00:43,650 --> 00:00:44,480
P set 7.

16
00:00:44,480 --> 00:00:48,400
>> And then we're going to talk a little
bit about how view controllers work

17
00:00:48,400 --> 00:00:54,640
and why that's a philosophy behind some
modern web pages and different design.

18
00:00:54,640 --> 00:00:58,760
Pretty much a lot of types of apps
and applications you might ship

19
00:00:58,760 --> 00:01:01,120
are using this model,
view controller framework,

20
00:01:01,120 --> 00:01:02,890
that you will be using
in P set 7, so I'll

21
00:01:02,890 --> 00:01:05,220
talk a little bit
about why that's become

22
00:01:05,220 --> 00:01:07,970
popular, why it's important and nice.

23
00:01:07,970 --> 00:01:12,052
And then I'll finally move on to
some tips about tackling P set 7.

24
00:01:12,052 --> 00:01:13,760
And if we have time
left over at the end,

25
00:01:13,760 --> 00:01:17,320
we can actually do some
work on that together.

26
00:01:17,320 --> 00:01:20,380
>> So, PHP.

27
00:01:20,380 --> 00:01:23,790
In fact, you may have noticed this--
you didn't really have to dive into it--

28
00:01:23,790 --> 00:01:27,880
but P set 6 had some PHP
code that was going on.

29
00:01:27,880 --> 00:01:34,710
And because PHP is a C-like
language, PHP, unlike HTML and CSS,

30
00:01:34,710 --> 00:01:39,030
is a programming language,
whereas HTML and CSS are static.

31
00:01:39,030 --> 00:01:44,050
They're markup languages dealing
with style and visual layout.

32
00:01:44,050 --> 00:01:46,230
PHP is the real deal.

33
00:01:46,230 --> 00:01:51,590
>> PHP has loops, it has conditions--
all that stuff that's fun about C.

34
00:01:51,590 --> 00:01:56,190
It has a few things that are a little
bit better than C, which we'll see,

35
00:01:56,190 --> 00:01:59,760
but I think the easiest way to talk
about the PHP is just to dive in.

36
00:01:59,760 --> 00:02:04,087
So I'm going to go right
into the IDE at this point.

37
00:02:04,087 --> 00:02:06,170
The first thing we're going
to do is actually look

38
00:02:06,170 --> 00:02:10,169
a little bit at some of the
PHP code that was in P set 6.

39
00:02:10,169 --> 00:02:13,600
So the way that we do that--
before, the way that we were running

40
00:02:13,600 --> 00:02:18,550
the server for the appliance
was that we would have to type--

41
00:02:18,550 --> 00:02:21,750
either use your implementation
or the staff's implementation

42
00:02:21,750 --> 00:02:27,059
of server.c by going into directory
and running server.c with either no

43
00:02:27,059 --> 00:02:30,100
arguments-- so just call it on the
local host, which is what you probably

44
00:02:30,100 --> 00:02:31,849
did most of the time--
and then feeding it

45
00:02:31,849 --> 00:02:35,380
a directory-- with
which to use as its root

46
00:02:35,380 --> 00:02:38,310
where the website would
be run, basically.

47
00:02:38,310 --> 00:02:42,180
>> This week for P set 7, as
great as our code for server.c

48
00:02:42,180 --> 00:02:47,580
is, there are people who have already
written these fine things over at CS50

49
00:02:47,580 --> 00:02:49,630
that have a little bit
more functionality,

50
00:02:49,630 --> 00:02:52,920
a server program that's capable
of dealing with a little more

51
00:02:52,920 --> 00:02:56,350
of the intricacies that we'll
see in both P set 7 and P set 8.

52
00:02:56,350 --> 00:03:01,410
And the way that you start up the
server is by just typing, "apache50."

53
00:03:01,410 --> 00:03:03,960
>> And before you do anything,
you want to make sure

54
00:03:03,960 --> 00:03:06,070
that Apache 50 is not
already running as it is

55
00:03:06,070 --> 00:03:08,130
on my machine, which I did to test it.

56
00:03:08,130 --> 00:03:10,320
And you do that by calling apache50.

57
00:03:10,320 --> 00:03:14,070
Stop, and you'll see that it's stopping
the web server, if you can look there

58
00:03:14,070 --> 00:03:16,340
at the bottom of the terminal window.

59
00:03:16,340 --> 00:03:21,090
And then just to start, we're
going to call, "apache50 start."

60
00:03:21,090 --> 00:03:23,150
And then we're going
to feed it a directory.

61
00:03:23,150 --> 00:03:26,950
>> Now, because we want to look
at some of the P set 6 code

62
00:03:26,950 --> 00:03:32,850
that we had implemented, I actually
copied a little bit of the P

63
00:03:32,850 --> 00:03:37,090
set 6 code into my own folder,
which you can see on the left there.

64
00:03:37,090 --> 00:03:40,170
It's called "SECTION8"
in all capital letters

65
00:03:40,170 --> 00:03:44,510
because I'm just so excited
to be live-streamed today.

66
00:03:44,510 --> 00:03:47,330
>> So if we run this, it should
all work pretty effectively.

67
00:03:47,330 --> 00:03:52,350
It says, OK, our site is now
available at the address of the IDE,

68
00:03:52,350 --> 00:03:57,710
basically, which is what you were using
exactly as it was in P set 7-- P set 6.

69
00:03:57,710 --> 00:04:00,899
All my indexes are one index today.

70
00:04:00,899 --> 00:04:02,940
So we can go to that
address, if you'll remember,

71
00:04:02,940 --> 00:04:05,710
by just clicking this little
button in the upper right.

72
00:04:05,710 --> 00:04:14,200
>> And you'll recall this code, which
happened when you went into hello.php.

73
00:04:14,200 --> 00:04:18,000
And what the code is designed to
do is when you typed in a name

74
00:04:18,000 --> 00:04:20,550
here-- if you say Sam
because that's my name--

75
00:04:20,550 --> 00:04:23,620
and I click Say Hello, when
we went to the next page,

76
00:04:23,620 --> 00:04:25,270
that name was supposed to be displayed.

77
00:04:25,270 --> 00:04:28,550
It would say, "Hello, Sam"
or "Hello," whatever name you

78
00:04:28,550 --> 00:04:32,470
put into it even though we went
to an entirely new web page.

79
00:04:32,470 --> 00:04:36,610
>> And this is the sort of thing
that PHP can do for you.

80
00:04:36,610 --> 00:04:42,840
PHP is able to pass data
between two web pages.

81
00:04:42,840 --> 00:04:44,390
This is a totally different page.

82
00:04:44,390 --> 00:04:46,990
You'll see the title is "hello" here.

83
00:04:46,990 --> 00:04:49,080
Actually, they have
the same title, but I

84
00:04:49,080 --> 00:04:52,560
promise they are different web
pages if we look at the source.

85
00:04:52,560 --> 00:04:55,890
And you can pass the data that's
entered in this text field,

86
00:04:55,890 --> 00:04:59,830
you submit it to the next
page that's being called up,

87
00:04:59,830 --> 00:05:02,490
and then that data is able to
be there in its present form.

88
00:05:02,490 --> 00:05:04,810
>> Now we haven't yet implemented
this ourselves, which

89
00:05:04,810 --> 00:05:08,710
is what we're going to do right now to
sort get a flavor for how PHP works,

90
00:05:08,710 --> 00:05:15,070
but the key idea is that PHP-- you can
sort of think of it like a function.

91
00:05:15,070 --> 00:05:18,570
Something that PHP can let you
do is it can take parameters

92
00:05:18,570 --> 00:05:24,710
that you input into an HTML page
through the use of PHP and forms,

93
00:05:24,710 --> 00:05:29,960
and it can pass those as parameters
to the next page that it loads up.

94
00:05:29,960 --> 00:05:35,110
>> In this case, we're loading up this
page with the "Say hello" button.

95
00:05:35,110 --> 00:05:38,960
But for now, I actually
deleted some of that code

96
00:05:38,960 --> 00:05:44,850
in the hello.php that was being run
that was actually displaying the "hello,

97
00:05:44,850 --> 00:05:49,680
world" or "hello, Sam" or
"hello," whatever was just input.

98
00:05:49,680 --> 00:05:53,620
So for right now, we're
going to do that, basically.

99
00:05:53,620 --> 00:05:56,570
We're going to recreate that and
also add some more functionality,

100
00:05:56,570 --> 00:06:00,210
do a little bit more with it, see
what PHP is really capable of.

101
00:06:00,210 --> 00:06:04,870
>> So first, let's talk about
this file, hello.php.

102
00:06:04,870 --> 00:06:07,440
So if we zoom in a
little bit-- and now I'm

103
00:06:07,440 --> 00:06:10,520
sort of trying to scroll all
the way around-- there we go.

104
00:06:10,520 --> 00:06:14,220
You'll see it's called
hello.php, but the syntax of it

105
00:06:14,220 --> 00:06:16,880
looks like an HTML file.

106
00:06:16,880 --> 00:06:20,380
This is because the
actual PHP in this file

107
00:06:20,380 --> 00:06:25,220
is all stuck between these
question mark-caret blocks.

108
00:06:25,220 --> 00:06:28,610
Everything right here
is considered PHP code.

109
00:06:28,610 --> 00:06:32,040
>> And you'll notice that
when I did a comment,

110
00:06:32,040 --> 00:06:35,320
you'll see the familiar
two forward slashes.

111
00:06:35,320 --> 00:06:38,440
And if you'll recall, in
HTML, if I type a comment,

112
00:06:38,440 --> 00:06:42,540
it looks something closer to
this, which is a comment in HTML.

113
00:06:42,540 --> 00:06:46,570
So really everything between
these two angle brackets

114
00:06:46,570 --> 00:06:50,060
is now PHP code, which
is reflected in the fact

115
00:06:50,060 --> 00:06:53,270
that this little comment symbol
is turned into a comment.

116
00:06:53,270 --> 00:06:58,420
>> So every time you write PHP code, even
if there's no HTML code outside of it,

117
00:06:58,420 --> 00:07:02,720
it's always going to be
enclosed in these angle brackets

118
00:07:02,720 --> 00:07:04,080
with question marks.

119
00:07:04,080 --> 00:07:08,260
You can sort of think about it-- how all
of the code that ran in your C programs

120
00:07:08,260 --> 00:07:13,950
was enclosed in an int main, void,
curly brace, end curly brace statement.

121
00:07:13,950 --> 00:07:17,100
And you'll see curly braces in
PHP, too, but this is sort of

122
00:07:17,100 --> 00:07:20,490
like the main method of PHP.

123
00:07:20,490 --> 00:07:25,630
>> So now, how do we do anything in PHP?

124
00:07:25,630 --> 00:07:29,190
Now, PHP is a programming
language that's very C-like,

125
00:07:29,190 --> 00:07:30,970
but it operates on the web.

126
00:07:30,970 --> 00:07:33,270
So one thing that
you'll immediately-- one

127
00:07:33,270 --> 00:07:38,130
of the first things you really did with
C was you printed stuff out, right?

128
00:07:38,130 --> 00:07:42,290
So in C we did that
with a printf function.

129
00:07:42,290 --> 00:07:46,430
We gave it a string,
probably with a new line,

130
00:07:46,430 --> 00:07:49,850
and then we terminated
it with a semicolon.

131
00:07:49,850 --> 00:07:53,790
>> So the way that we're going to do that
in PHP-- because it's not quite printf.

132
00:07:53,790 --> 00:07:55,940
It's a little bit of different syntax.

133
00:07:55,940 --> 00:08:02,580
The way that we print things out
in PHP is we say, "echo hello"

134
00:08:02,580 --> 00:08:04,180
or "echo" any word.

135
00:08:04,180 --> 00:08:09,830
And that has the effect of doing
printf with a string, "hello."

136
00:08:09,830 --> 00:08:11,990
And it adds the new line to it.

137
00:08:11,990 --> 00:08:16,000
>> So let's right now make sure--
I'll zoom out again a little bit--

138
00:08:16,000 --> 00:08:18,250
let's make sure that
that code is working

139
00:08:18,250 --> 00:08:21,030
because there might very
well be a bug in this code

140
00:08:21,030 --> 00:08:22,880
that we will have to tackle.

141
00:08:22,880 --> 00:08:25,860
So the server is already running.

142
00:08:25,860 --> 00:08:30,630
So if we scroll back down to the bottom,
yup, the server is still running.

143
00:08:30,630 --> 00:08:34,510
So if we just tap on this
little bit right here--

144
00:08:34,510 --> 00:08:37,620
welcome-- we should get-- great.

145
00:08:37,620 --> 00:08:39,930
>> We still are having the
familiar "Say hello" dialogue,

146
00:08:39,930 --> 00:08:45,750
but when I type in "hi," we'll see
that the text "hello" was indeed

147
00:08:45,750 --> 00:08:50,080
printed out, which is exactly as
we expected because echo in PHP

148
00:08:50,080 --> 00:08:53,190
is just like a printf statement.

149
00:08:53,190 --> 00:09:01,410
So back to the code, how in P set 6 did
the distribution code you are provided

150
00:09:01,410 --> 00:09:05,920
make it so that PHP would
output the thing that you

151
00:09:05,920 --> 00:09:07,920
typed in on the previous screen?

152
00:09:07,920 --> 00:09:10,350
>> And to sort of examine
why that happens, we're

153
00:09:10,350 --> 00:09:15,510
going to go into index.html, which
is the original file, the file that

154
00:09:15,510 --> 00:09:18,710
shows up on this screen
with the "Say hello" button.

155
00:09:18,710 --> 00:09:20,950
You notice that there's
all the classic things

156
00:09:20,950 --> 00:09:26,910
we've come to expect from HTML such
as these things, these tags enclosed

157
00:09:26,910 --> 00:09:31,080
in angle brackets, like PHP
but without the question marks,

158
00:09:31,080 --> 00:09:34,650
which indicates a special thing to HTML.

159
00:09:34,650 --> 00:09:36,895
We have title, which is "hello."

160
00:09:36,895 --> 00:09:41,010
And you'll notice that as we saw,
the title is "hello" in both cases.

161
00:09:41,010 --> 00:09:43,260
Let's change this one
to "say" just so we

162
00:09:43,260 --> 00:09:48,170
can distinguish ourselves where we are.

163
00:09:48,170 --> 00:09:49,600
>> But we've got a body.

164
00:09:49,600 --> 00:09:52,690
And then the interesting bit, the
bit that shows up in the HTML,

165
00:09:52,690 --> 00:09:54,530
is this form element.

166
00:09:54,530 --> 00:09:56,370
And so we've got a form.

167
00:09:56,370 --> 00:09:58,330
And this is the key.

168
00:09:58,330 --> 00:10:00,530
This is how we're working with PHP.

169
00:10:00,530 --> 00:10:05,790
The action parameter of
form says that hello.php

170
00:10:05,790 --> 00:10:09,310
is what we're going to send
the values in this form to.

171
00:10:09,310 --> 00:10:13,830
This is where we're passing
the parameters, so to speak.

172
00:10:13,830 --> 00:10:18,680
>> You'll notice another thing here
is that the method is "get."

173
00:10:18,680 --> 00:10:24,450
There are two primary
methods by which will

174
00:10:24,450 --> 00:10:28,750
be using PHP to pass data
between websites-- web pages,

175
00:10:28,750 --> 00:10:30,500
rather-- in this assignment.

176
00:10:30,500 --> 00:10:34,070
And those methods are "get" and "post."

177
00:10:34,070 --> 00:10:37,010
There are some subtle
differences between get and post

178
00:10:37,010 --> 00:10:40,520
that we will get into-- we
will "get" into, if you will.

179
00:10:40,520 --> 00:10:44,030
>> But for all intents and
purposes, get and post

180
00:10:44,030 --> 00:10:47,120
are both just ways that
you pass parameters

181
00:10:47,120 --> 00:10:49,500
with slightly different executions.

182
00:10:49,500 --> 00:10:53,500
For now, we're going to use get because
get was what was used originally

183
00:10:53,500 --> 00:10:57,340
in the PHP file of P set 6.

184
00:10:57,340 --> 00:11:00,850
And actually, if we go in and look
before we've edited anything else,

185
00:11:00,850 --> 00:11:03,090
I'm going to say hi
to-- what's your name?

186
00:11:03,090 --> 00:11:03,812
>> AUDIENCE: Elliot.

187
00:11:03,812 --> 00:11:04,770
SAM LEVATICH: Oh, gosh.

188
00:11:04,770 --> 00:11:05,600
I don't know how to spell that.

189
00:11:05,600 --> 00:11:06,766
Could you spell that for me?

190
00:11:06,766 --> 00:11:08,710
AUDIENCE: E-L-L-I-O-T.

191
00:11:08,710 --> 00:11:09,720
>> SAM LEVATICH: I-O-T?

192
00:11:09,720 --> 00:11:10,440
>> AUDIENCE: Yeah.

193
00:11:10,440 --> 00:11:10,960
>> SAM LEVATICH: Perfect.

194
00:11:10,960 --> 00:11:11,210
OK.

195
00:11:11,210 --> 00:11:12,751
I guess I did know how to spell that.

196
00:11:12,751 --> 00:11:13,510
Sorry about that.

197
00:11:13,510 --> 00:11:16,560
But if we say "Say hello," it's not
it's not going to show up on the screen

198
00:11:16,560 --> 00:11:18,476
yet because we modified
the code a little bit.

199
00:11:18,476 --> 00:11:21,290
But if we do "Say hello"--
OK, so "hello" is here.

200
00:11:21,290 --> 00:11:24,137
But if we take a closer
look at the URL itself,

201
00:11:24,137 --> 00:11:26,220
we'll see that it ends
with hello.php?name=Elliot.

202
00:11:26,220 --> 00:11:30,980

203
00:11:30,980 --> 00:11:37,180
>> So, this is a way of
communicating to the next web page

204
00:11:37,180 --> 00:11:39,240
the parameters that we've passed.

205
00:11:39,240 --> 00:11:40,870
We said name=Elliot.

206
00:11:40,870 --> 00:11:46,290
And that's ultimately how P set 6
accessed the variable that we passed in

207
00:11:46,290 --> 00:11:47,520
through the form.

208
00:11:47,520 --> 00:11:51,470
And this is something that
is peculiar to a get request.

209
00:11:51,470 --> 00:11:57,480
A get request makes the parameters
known in the URL of the website.

210
00:11:57,480 --> 00:12:01,190
>> And you'll recall, too,
in P set 6 that you

211
00:12:01,190 --> 00:12:04,450
had to write a function
that dealt with the fact

212
00:12:04,450 --> 00:12:09,700
that this query string
could exist after a file.

213
00:12:09,700 --> 00:12:14,684
There could be a question mark followed
by basically any number of characters.

214
00:12:14,684 --> 00:12:16,350
And that's exactly what's going on here.

215
00:12:16,350 --> 00:12:21,280
And the reason you had to parse that
in your implementation of server.c in P

216
00:12:21,280 --> 00:12:27,570
set 6 is so that you could tell
the PHP code that name=Elliot.

217
00:12:27,570 --> 00:12:30,460
You needed to be able to
parse that out of the URL

218
00:12:30,460 --> 00:12:35,900
so that the PHP file in question
knew what it was dealing with.

219
00:12:35,900 --> 00:12:39,350
>> So hopefully this gives
the motivation to server.c

220
00:12:39,350 --> 00:12:43,900
now that we're moving on
outside of C into PHP.

221
00:12:43,900 --> 00:12:48,240
So let's actually focus on accessing the
things passed through a get request now

222
00:12:48,240 --> 00:12:48,880
at this point.

223
00:12:48,880 --> 00:12:50,157
I'm going to save this.

224
00:12:50,157 --> 00:12:51,240
We didn't change anything.

225
00:12:51,240 --> 00:12:56,080
It looks like we've got a input field.

226
00:12:56,080 --> 00:12:58,550
>> We're setting some properties,
as we can do an HTML.

227
00:12:58,550 --> 00:12:59,550
These are simple things.

228
00:12:59,550 --> 00:13:00,580
We don't need these.

229
00:13:00,580 --> 00:13:03,750
But we've got autocomplete off,
which basically says-- you know,

230
00:13:03,750 --> 00:13:05,710
when you type things
into the web, sometimes

231
00:13:05,710 --> 00:13:07,355
it tries to fill that in for you.

232
00:13:07,355 --> 00:13:08,230
So it's a nice thing.

233
00:13:08,230 --> 00:13:11,700
We want to turn it off for this purpose.

234
00:13:11,700 --> 00:13:13,970
That was a CS50 decision.

235
00:13:13,970 --> 00:13:15,640
So we can delete that if we wanted.

236
00:13:15,640 --> 00:13:19,510
>> Autofocus just sticks the cursor
in the form right at the beginning.

237
00:13:19,510 --> 00:13:21,060
Again, not too important.

238
00:13:21,060 --> 00:13:26,220
>> But name="name"-- it's a little
tricky because it's name and name.

239
00:13:26,220 --> 00:13:28,730
But we could've changed
this to something else.

240
00:13:28,730 --> 00:13:30,563
And in fact, that's
what we'll do right now.

241
00:13:30,563 --> 00:13:34,830
We'll say "person," which
is sort of like name

242
00:13:34,830 --> 00:13:36,790
if a person is defined by their name.

243
00:13:36,790 --> 00:13:41,480
>> So let's close this,
reopen up our website

244
00:13:41,480 --> 00:13:46,110
since our server is still running
Apache 50, and we'll say, hello, here's

245
00:13:46,110 --> 00:13:47,200
Elliot again.

246
00:13:47,200 --> 00:13:48,460
Why not?

247
00:13:48,460 --> 00:13:49,220
Hello.

248
00:13:49,220 --> 00:13:52,880
And if we go up here, we'll see
then instead of name=Elliot,

249
00:13:52,880 --> 00:13:55,200
it says person=Elliot.

250
00:13:55,200 --> 00:14:00,060
And that's a direct result of the fact
that we just changed name="person."

251
00:14:00,060 --> 00:14:06,840
>> So in an input element of
an HTML form, the name field

252
00:14:06,840 --> 00:14:10,590
is the identifier for the
parameter that's being passed.

253
00:14:10,590 --> 00:14:14,250
It's like if you're creating a function
"add" that took in two integers

254
00:14:14,250 --> 00:14:16,670
and you said int a and int b.

255
00:14:16,670 --> 00:14:22,680
That would be name a, and if
you wanted another form, which

256
00:14:22,680 --> 00:14:27,800
we can do just by copying and
pasting, then we would have name b.

257
00:14:27,800 --> 00:14:31,030
>> So now we'll have two parameters
that are being passed through

258
00:14:31,030 --> 00:14:36,970
get to the next website--
the next web page, hello.php.

259
00:14:36,970 --> 00:14:39,770
And we can actually see
that again if we want.

260
00:14:39,770 --> 00:14:44,830
This is the easiest way to deal with
the web code in the IDE, basically.

261
00:14:44,830 --> 00:14:47,940
You start up the server, get it
running, and then every time you

262
00:14:47,940 --> 00:14:50,649
make some changes, just close
that file just to be safe.

263
00:14:50,649 --> 00:14:52,440
Pressing the back button
is a little tricky

264
00:14:52,440 --> 00:14:55,800
because it might load an earlier
version, not the most updated one.

265
00:14:55,800 --> 00:14:59,200
>> And then you just click your
button again, pop right up-- oh,

266
00:14:59,200 --> 00:15:00,510
and now there are two forms.

267
00:15:00,510 --> 00:15:10,440
And so if we type one thing into each
one-- "jason hirshhorn," for instance--

268
00:15:10,440 --> 00:15:11,590
we say hello.

269
00:15:11,590 --> 00:15:12,840
We look up at our parameters.

270
00:15:12,840 --> 00:15:18,910
It looks like we've got, as
expected, a=jason and b=hirshhorn,

271
00:15:18,910 --> 00:15:23,760
which represents the two parameters
that we passed to this function.

272
00:15:23,760 --> 00:15:27,900
>> So now let's actually get to
implementing that functionality that we

273
00:15:27,900 --> 00:15:30,840
had in P set 6.

274
00:15:30,840 --> 00:15:32,490
So right now we're just echoing hello.

275
00:15:32,490 --> 00:15:34,310
And that's not very useful.

276
00:15:34,310 --> 00:15:38,530
We want to echo some variable
that was passed to us.

277
00:15:38,530 --> 00:15:40,320
And we know the name of this variable.

278
00:15:40,320 --> 00:15:41,770
We have a and we have b.

279
00:15:41,770 --> 00:15:43,500
So we could choose to echo either one.

280
00:15:43,500 --> 00:15:45,470
>> But how do we access it?

281
00:15:45,470 --> 00:15:48,820
Well, there are certain
global variables in PHP.

282
00:15:48,820 --> 00:15:51,240
And I'm going to write
them in comments here.

283
00:15:51,240 --> 00:15:59,910
The two most important ones are get
and post for our purposes right now.

284
00:15:59,910 --> 00:16:05,350
These are the arrays or,
technically, the dictionaries

285
00:16:05,350 --> 00:16:10,540
where our variables that we're
passing to the next web page live.

286
00:16:10,540 --> 00:16:14,520
And we shall soon see how to use them.

287
00:16:14,520 --> 00:16:19,720
>> Another brief note about PHP code
and some specifics of it-- in C,

288
00:16:19,720 --> 00:16:23,260
to declare a variable
or to use variables,

289
00:16:23,260 --> 00:16:24,570
you first had to declare them.

290
00:16:24,570 --> 00:16:30,860
And what you had to do when you
declared them was say int a or char b.

291
00:16:30,860 --> 00:16:35,630
You had to declare the types of these
variables before you created them.

292
00:16:35,630 --> 00:16:38,800
PHP-- you don't need to do any of that.

293
00:16:38,800 --> 00:16:42,522
PHP does not ask for
the type of variable.

294
00:16:42,522 --> 00:16:44,480
And the way that you
create a variable-- rather

295
00:16:44,480 --> 00:16:49,930
than saying int, char, string--
which is really char *, as we know--

296
00:16:49,930 --> 00:16:52,180
rather than doing all of
that, because everything

297
00:16:52,180 --> 00:16:54,620
is of the same type,
typeless, we can just

298
00:16:54,620 --> 00:16:59,210
use one character, which
is the dollar sign.

299
00:16:59,210 --> 00:17:03,700
And you'll see it's already popping
up, little autocomplete things.

300
00:17:03,700 --> 00:17:11,380
And it's saying that _GET and _POST
are two options that I have available

301
00:17:11,380 --> 00:17:11,900
to me.

302
00:17:11,900 --> 00:17:16,430
Some of these other things are
other global variables in PHP

303
00:17:16,430 --> 00:17:18,430
that you'll be using over
the course of P set 7.

304
00:17:18,430 --> 00:17:20,569
For now we're going to
focus on get and post.

305
00:17:20,569 --> 00:17:22,910
But this is a helpful
thing that the IDE does

306
00:17:22,910 --> 00:17:24,980
where once you've typed
in that dollar sign,

307
00:17:24,980 --> 00:17:28,760
it'll start filling in global variables
or variables you've already defined.

308
00:17:28,760 --> 00:17:34,360
>> So if you wanted to define
a variable called "string,"

309
00:17:34,360 --> 00:17:38,290
you could just set it equal to "hi."

310
00:17:38,290 --> 00:17:40,100
And it's basically as simple as that.

311
00:17:40,100 --> 00:17:44,720
And then we could do
something like "echo $string."

312
00:17:44,720 --> 00:17:48,524
The IDE should be throwing some
errors if I'm doing anything wrong,

313
00:17:48,524 --> 00:17:50,190
so hopefully I'm doing everything right.

314
00:17:50,190 --> 00:17:52,060
But bugs always do arise.

315
00:17:52,060 --> 00:17:56,670
>> Another tricky thing about
PHP is that it's not compiled.

316
00:17:56,670 --> 00:18:00,640
So with C programs, you would do
the daily routine of-- basically,

317
00:18:00,640 --> 00:18:02,710
you would make edits to
your code, you'd save it,

318
00:18:02,710 --> 00:18:04,460
and then you would
make it, where make was

319
00:18:04,460 --> 00:18:08,830
the step that called the compiler,
clang, to make your code, this text

320
00:18:08,830 --> 00:18:10,570
file, into an executable.

321
00:18:10,570 --> 00:18:15,550
PHP is C-like, but it's executed
on the fly by your web browser.

322
00:18:15,550 --> 00:18:17,640
So there's no way to know.

323
00:18:17,640 --> 00:18:19,790
>> Make would throw those
helpful errors, right?

324
00:18:19,790 --> 00:18:22,190
It would be like, you
didn't declare this variable

325
00:18:22,190 --> 00:18:23,320
before you tried to use it.

326
00:18:23,320 --> 00:18:29,120
You did all this bad stuff-- segfault,
segfault, all that sort of fun times

327
00:18:29,120 --> 00:18:31,000
that came with make.

328
00:18:31,000 --> 00:18:33,920
PHP is a double-edged sword
because you won't get those errors,

329
00:18:33,920 --> 00:18:37,770
but that also means that you won't know
really what's wrong with your program

330
00:18:37,770 --> 00:18:39,840
if you just run it and it's not working.

331
00:18:39,840 --> 00:18:45,130
But the debugger should point out
some hopefully helpful little things

332
00:18:45,130 --> 00:18:47,950
syntactically that you can fix.

333
00:18:47,950 --> 00:18:52,850
>> So now if we go over to--
say, let's close that.

334
00:18:52,850 --> 00:18:54,522
Reopen.

335
00:18:54,522 --> 00:18:55,480
And we're back to here.

336
00:18:55,480 --> 00:18:57,210
So we've got a variable
and a variable b.

337
00:18:57,210 --> 00:18:58,626
And these won't ultimately matter.

338
00:18:58,626 --> 00:19:01,850
We'll call them h and g
for no particular reason.

339
00:19:01,850 --> 00:19:03,120
>> And we say hello.

340
00:19:03,120 --> 00:19:07,480
Now it looks like our string
"hi" is indeed printing.

341
00:19:07,480 --> 00:19:10,460
We created a variable called
"string," set it equal to "hi."

342
00:19:10,460 --> 00:19:15,520
Notice that we didn't have to do
malloc or make a character array.

343
00:19:15,520 --> 00:19:19,110
>> In PHP, because variables
are typeless, a string

344
00:19:19,110 --> 00:19:22,230
is the same as a char for
all intents and purposes.

345
00:19:22,230 --> 00:19:23,570
This could be "hi."

346
00:19:23,570 --> 00:19:26,340
This could be just the character k.

347
00:19:26,340 --> 00:19:29,290
This can be a number 1.

348
00:19:29,290 --> 00:19:30,300
And it doesn't care.

349
00:19:30,300 --> 00:19:33,560
PHP doesn't care about
the type of your variable.

350
00:19:33,560 --> 00:19:34,390
Or, it does care.

351
00:19:34,390 --> 00:19:36,240
It cares when you try
and do things with it,

352
00:19:36,240 --> 00:19:38,790
but it does not care in
the declaration step.

353
00:19:38,790 --> 00:19:46,960
>> And just like you can in C, you can
declare strings on the stack like this

354
00:19:46,960 --> 00:19:51,130
though saying "stack" is a little
bit of a potential misnomer when

355
00:19:51,130 --> 00:19:52,230
we're talking about PHP.

356
00:19:52,230 --> 00:19:54,020
But we don't have to worry about that.

357
00:19:54,020 --> 00:19:55,936
So we got our string
"hi," and we echo string.

358
00:19:55,936 --> 00:19:58,880
So now we've discussed variables.

359
00:19:58,880 --> 00:20:06,060
So now we need to talk about get and
post and perform the final thing that's

360
00:20:06,060 --> 00:20:12,660
needed to really get this back up
to the functionality of the P set 6.

361
00:20:12,660 --> 00:20:14,990
So right now we're
echoing the string, but we

362
00:20:14,990 --> 00:20:17,080
do have these variables get and post.

363
00:20:17,080 --> 00:20:19,430
And because we're using
the method get, it

364
00:20:19,430 --> 00:20:24,810
seems natural that our variable that
we're interested in, both a and b,

365
00:20:24,810 --> 00:20:29,870
will be located in the array
or dictionary, technically get.

366
00:20:29,870 --> 00:20:33,510
>> So if we set up get like this
with your groups-- I pressed enter

367
00:20:33,510 --> 00:20:36,770
and it didn't like it--
but here we have get.

368
00:20:36,770 --> 00:20:38,000
And so get already exists.

369
00:20:38,000 --> 00:20:41,380
So we can already start to access
some of the elements of get.

370
00:20:41,380 --> 00:20:45,000
If we do get, this syntax for
arrays in PHP is very C-like.

371
00:20:45,000 --> 00:20:47,900
We have our two square brackets.

372
00:20:47,900 --> 00:20:53,440
>> So if we say get in a normal
array, we could access

373
00:20:53,440 --> 00:20:55,600
the zeroth index, the first index.

374
00:20:55,600 --> 00:20:56,840
PHP is zero index.

375
00:20:56,840 --> 00:21:00,550
We could say zero, one,
two-- stuff like this.

376
00:21:00,550 --> 00:21:03,420
And I've been saying that get
is technically a dictionary.

377
00:21:03,420 --> 00:21:08,290
So what PHP is doing under the hood,
which is a little bit nicer than C,

378
00:21:08,290 --> 00:21:12,760
is it already is giving you some
dictionary functionality, which

379
00:21:12,760 --> 00:21:16,240
is really hash tables,
or tries to, supposedly.

380
00:21:16,240 --> 00:21:19,360
Or, technically it
could be a try as well.

381
00:21:19,360 --> 00:21:25,500
But PHP is implementing a hash table,
which forms an effective dictionary.

382
00:21:25,500 --> 00:21:28,400
>> And so we know the name
of our variable, right?

383
00:21:28,400 --> 00:21:32,440
It's being passed in
the query string by PHP.

384
00:21:32,440 --> 00:21:37,290
We have a=h and b=g where and b
are the names of the variables.

385
00:21:37,290 --> 00:21:41,580
So the way that we can access the
value that corresponds to the key

386
00:21:41,580 --> 00:21:45,055
in our dictionary is
just by saying _GET_GET["a"].

387
00:21:45,055 --> 00:21:48,170

388
00:21:48,170 --> 00:21:51,365
>> So now we have _GET["a"].

389
00:21:51,365 --> 00:21:56,930
And if we just replace inside
our echo, if we echo _GET_GET["a"]--

390
00:21:56,930 --> 00:22:02,410
and we'll see if the debugger
throws any errors about this--

391
00:22:02,410 --> 00:22:05,620
we'll save that and close this out.

392
00:22:05,620 --> 00:22:07,130
Open it up.

393
00:22:07,130 --> 00:22:10,390
So we're just doing a right
now, so b shouldn't matter.

394
00:22:10,390 --> 00:22:12,980
"her" and "him"--
"hum." "her" and "hum."

395
00:22:12,980 --> 00:22:14,810
Sounds good.

396
00:22:14,810 --> 00:22:18,040
>> And it printed out
"her," which is crazy.

397
00:22:18,040 --> 00:22:21,920
But that's exactly what
was happening in P set 6.

398
00:22:21,920 --> 00:22:27,240
Basically, what P set 6
was doing-- echo hello,

399
00:22:27,240 --> 00:22:31,580
name-- where it had a
variable name and it just

400
00:22:31,580 --> 00:22:35,520
asks you to type in that bit of text.

401
00:22:35,520 --> 00:22:37,380
There was also some
additional code where

402
00:22:37,380 --> 00:22:40,550
it included if statements,
which we can do right now.

403
00:22:40,550 --> 00:22:50,120
>> We can say if exists, which
is a functionality within PHP,

404
00:22:50,120 --> 00:22:55,110
_GET with the underscore, "name"--
which is basically saying,

405
00:22:55,110 --> 00:22:58,760
"if name has been filled in" because
we could have just clicked the button

406
00:22:58,760 --> 00:23:02,580
to submit the form without
typing anything into that field.

407
00:23:02,580 --> 00:23:07,760
And we wrap that in our
friendly curly braces.

408
00:23:07,760 --> 00:23:09,175
We can have an else statement.

409
00:23:09,175 --> 00:23:13,300

410
00:23:13,300 --> 00:23:18,820
And that's all within the PHP angle
bracket, question mark, angle bracket,

411
00:23:18,820 --> 00:23:20,040
if you will.

412
00:23:20,040 --> 00:23:21,750
>> And now we'll see if this works.

413
00:23:21,750 --> 00:23:26,300
I keep waiting for it to debug
and crap out on me, basically,

414
00:23:26,300 --> 00:23:28,410
but it hasn't yet.

415
00:23:28,410 --> 00:23:30,830
Maybe it will now
because I talked about.

416
00:23:30,830 --> 00:23:31,330
Yup.

417
00:23:31,330 --> 00:23:32,510
It did, in fact.

418
00:23:32,510 --> 00:23:34,610
So, nothing is showing up.

419
00:23:34,610 --> 00:23:38,750
That's because of something wrong
that I wrote in the PHP code.

420
00:23:38,750 --> 00:23:42,844
And I mentioned the debugging
is tricky because in PHP, we

421
00:23:42,844 --> 00:23:45,260
didn't compile it beforehand
and the compiler wasn't like,

422
00:23:45,260 --> 00:23:46,710
here's where your errors are.

423
00:23:46,710 --> 00:23:49,690
>> But what we can do
is-- do people remember

424
00:23:49,690 --> 00:23:57,010
how to look at the different network
requests that PHP-- or that websites

425
00:23:57,010 --> 00:23:57,620
send?

426
00:23:57,620 --> 00:24:00,290
[? Malin ?] did this in
lecture once or twice.

427
00:24:00,290 --> 00:24:05,830
You remember where we go to find
the different debts and 200 OKs,

428
00:24:05,830 --> 00:24:09,780
all these codes that are being sent
through HTTP from web page to web page?

429
00:24:09,780 --> 00:24:12,514
Does anyone remember
where we go to do that?

430
00:24:12,514 --> 00:24:13,787
>> AUDIENCE: Page Source.

431
00:24:13,787 --> 00:24:14,870
SAM LEVATICH: Page source.

432
00:24:14,870 --> 00:24:15,890
Exactly.

433
00:24:15,890 --> 00:24:19,230
If you go to Page Source-- perfect.

434
00:24:19,230 --> 00:24:21,630
So Page Source pulls up the inspector.

435
00:24:21,630 --> 00:24:23,140
>> And I'm using Safari.

436
00:24:23,140 --> 00:24:25,790
A lot of you will probably
be using Chrome or Firefox.

437
00:24:25,790 --> 00:24:27,750
But as long as you're
in any modern browser--

438
00:24:27,750 --> 00:24:29,500
and feel free to follow
along if you want.

439
00:24:29,500 --> 00:24:32,560
You can type up this code or
just look inside the P set 6

440
00:24:32,560 --> 00:24:35,820
directory for some similar stuff.

441
00:24:35,820 --> 00:24:41,020
hello.php is what we're
currently working on emulating.

442
00:24:41,020 --> 00:24:42,476
>> So there are a variety of tabs.

443
00:24:42,476 --> 00:24:43,850
We can look at all the resources.

444
00:24:43,850 --> 00:24:45,810
We can see the source code.

445
00:24:45,810 --> 00:24:49,900
So looks like it didn't
get past body in the end.

446
00:24:49,900 --> 00:24:54,890
It found an error in PHP and it
stopped loading the whole web page.

447
00:24:54,890 --> 00:24:58,320
We don't even have an end
tag for HTML or anything.

448
00:24:58,320 --> 00:25:07,189
>> And if we look at the network, we can
see that we're being sent a request.

449
00:25:07,189 --> 00:25:07,980
This is the domain.

450
00:25:07,980 --> 00:25:09,270
This is the address.

451
00:25:09,270 --> 00:25:10,070
It's a document.

452
00:25:10,070 --> 00:25:14,310
We're using the get method.

453
00:25:14,310 --> 00:25:15,760
>> And it's red.

454
00:25:15,760 --> 00:25:19,030
Or, it was red when I
wasn't selecting it.

455
00:25:19,030 --> 00:25:22,680
How do I unselect it?

456
00:25:22,680 --> 00:25:23,980
Well, it was red.

457
00:25:23,980 --> 00:25:25,201
Let me refresh.

458
00:25:25,201 --> 00:25:25,700
There it is.

459
00:25:25,700 --> 00:25:26,640
Now it's red.

460
00:25:26,640 --> 00:25:30,530
>> So it's red, which means
it failed, which is bad.

461
00:25:30,530 --> 00:25:32,280
So let's examine why it did fail.

462
00:25:32,280 --> 00:25:37,070
So all that the Page Source can
basically tell you is your thing

463
00:25:37,070 --> 00:25:38,720
didn't work, which we can already see.

464
00:25:38,720 --> 00:25:42,100
So ideally there would
be a more useful tool.

465
00:25:42,100 --> 00:25:45,710
And there are some browser extensions
that allow you to debug PHP,

466
00:25:45,710 --> 00:25:50,490
but we're not going to
be writing a ton of PHP,

467
00:25:50,490 --> 00:25:53,190
so it's probably just best
to look through your code

468
00:25:53,190 --> 00:25:56,760
carefully and just make sure that
it's not doing anything else.

469
00:25:56,760 --> 00:26:03,876
>> So let's see if the format of this
if statement is where the problem is.

470
00:26:03,876 --> 00:26:07,420
I want to load that back up here.

471
00:26:07,420 --> 00:26:09,830
Hello, hi.

472
00:26:09,830 --> 00:26:11,350
So there's a problem there.

473
00:26:11,350 --> 00:26:15,130
>> So for correct syntax
of PHP, PHP is going

474
00:26:15,130 --> 00:26:17,369
to be C-like in that you'll see loops.

475
00:26:17,369 --> 00:26:18,410
You'll see if statements.

476
00:26:18,410 --> 00:26:20,920
You'll see all these friends
that you've become familiar

477
00:26:20,920 --> 00:26:24,820
with over the course
of this CS50 semester.

478
00:26:24,820 --> 00:26:29,960
But the best way to figure out how to
do something in PHP is to Google it

479
00:26:29,960 --> 00:26:33,170
or to look at some examples of PHP code
because you know the functionality.

480
00:26:33,170 --> 00:26:35,080
>> You know what you can
do with the program.

481
00:26:35,080 --> 00:26:35,976
You can loop.

482
00:26:35,976 --> 00:26:37,600
You can loop as many times as you want.

483
00:26:37,600 --> 00:26:39,433
You can loop in all
sorts of different ways.

484
00:26:39,433 --> 00:26:40,700
You can create functions.

485
00:26:40,700 --> 00:26:43,241
You can create functions that
call other functions, functions

486
00:26:43,241 --> 00:26:44,150
that call themselves.

487
00:26:44,150 --> 00:26:45,733
And you have names for these concepts.

488
00:26:45,733 --> 00:26:49,860
You've got recursion, loops,
if, other control flows.

489
00:26:49,860 --> 00:26:51,300
And so Google is your best friend.

490
00:26:51,300 --> 00:26:53,540
Even say, "PHP if
statement" and there'll

491
00:26:53,540 --> 00:26:57,740
be tons of posts with
answers to other people

492
00:26:57,740 --> 00:27:02,090
who've had similar questions to you,
who are just starting out with PHP

493
00:27:02,090 --> 00:27:03,820
and are curious about a syntax thing.

494
00:27:03,820 --> 00:27:08,480
>> Because we have the luxury of being
able to look at the code in P set 6,

495
00:27:08,480 --> 00:27:14,980
we actually pull it up and see that
OK, here's something interesting.

496
00:27:14,980 --> 00:27:18,070
So this is what it actually
looked like in P set 6.

497
00:27:18,070 --> 00:27:20,340
So if we go through this,
we can see that we've

498
00:27:20,340 --> 00:27:27,150
got several of these little
PHP-like question mark bits.

499
00:27:27,150 --> 00:27:29,050
>> And there aren't curly braces.

500
00:27:29,050 --> 00:27:30,250
There are colons.

501
00:27:30,250 --> 00:27:32,340
And there are curly
braces in PHP, but this

502
00:27:32,340 --> 00:27:38,700
is a format and a way of doing
PHP that works well with HTML

503
00:27:38,700 --> 00:27:43,830
because as you'll see, we're closing
off these PHP bits-- the elses

504
00:27:43,830 --> 00:27:49,770
and the ifs and all of that-- and then
we're interspersing HTML inside them

505
00:27:49,770 --> 00:27:54,640
while still following the
control flow set out by PHP.

506
00:27:54,640 --> 00:27:58,480
>> So I'm just going to
quick walk through this

507
00:27:58,480 --> 00:28:01,740
because it's a lot of the same
concepts that we were doing before.

508
00:28:01,740 --> 00:28:07,280
We've got if not empty,
parentheses, _GET_GET["name"].

509
00:28:07,280 --> 00:28:08,500
This is all the same stuff.

510
00:28:08,500 --> 00:28:15,430
We're using the _GET dictionary that
PHP sends upon request of forms,

511
00:28:15,430 --> 00:28:20,720
because it is the parameters of
action, and the method is get.

512
00:28:20,720 --> 00:28:22,110
And then that ends that.

513
00:28:22,110 --> 00:28:27,420
The colon is a signifier to just do this
if the if statement evaluates to true.

514
00:28:27,420 --> 00:28:29,490
It's like a curly brace.

515
00:28:29,490 --> 00:28:33,320
And in fact, it is a curly brace
in other languages like Python,

516
00:28:33,320 --> 00:28:37,070
which you may encounter if you just
do that for your final project.

517
00:28:37,070 --> 00:28:40,170
>> And then this line, hello.

518
00:28:40,170 --> 00:28:41,510
Then we've got this weird thing.

519
00:28:41,510 --> 00:28:43,190
We've got more brackets.

520
00:28:43,190 --> 00:28:46,140
There's no HTTP there-- or PHP, sorry.

521
00:28:46,140 --> 00:28:47,250
But there's an equal sign.

522
00:28:47,250 --> 00:28:50,625
And then we have a function,
htmlspecialchars(_GEThtmlspecialchars(_GET["name"]).

523
00:28:50,625 --> 00:28:54,440

524
00:28:54,440 --> 00:28:58,040
This is sort of like a more
advanced version of echo.

525
00:28:58,040 --> 00:29:01,450
Like we had echo as a way
to print things out in PHP.

526
00:29:01,450 --> 00:29:03,890
This is a function that's
defined in PHP that

527
00:29:03,890 --> 00:29:08,160
will deal with some more nasty
characters and byte values

528
00:29:08,160 --> 00:29:09,540
that you could pass it.

529
00:29:09,540 --> 00:29:11,070
It's always safest to use this.

530
00:29:11,070 --> 00:29:14,930
But echo will do the job
just fine if we're not

531
00:29:14,930 --> 00:29:17,620
dealing with anything too nasty.

532
00:29:17,620 --> 00:29:20,340
>> And so this has the same
effect of basically,

533
00:29:20,340 --> 00:29:26,360
this stuff in between the question
marks is evaluated by PHP.

534
00:29:26,360 --> 00:29:34,490
htmlspecialchars returns a nice HTML
printed value of _GET_GET["name"], i.e.

535
00:29:34,490 --> 00:29:36,010
whatever we typed in the form.

536
00:29:36,010 --> 00:29:40,025
And then it'll say hello,
comma space, and then that.

537
00:29:40,025 --> 00:29:42,910
That whole thing between
the angle brackets

538
00:29:42,910 --> 00:29:47,390
will be replaced by whatever
htmlspecialchars puts out.

539
00:29:47,390 --> 00:29:49,390
So that's basically similar
to what we're doing.

540
00:29:49,390 --> 00:29:54,760
And we have an else statement that's
hello world, which makes sense.

541
00:29:54,760 --> 00:29:58,070
So now let's go back to our
code and see exactly-- oh.

542
00:29:58,070 --> 00:30:02,200
I said exists, which is not
a thing that we wanted to do.

543
00:30:02,200 --> 00:30:05,370
We wanted to say not empty.

544
00:30:05,370 --> 00:30:10,020
>> And so this should work a little
bit better, not empty _GET_GET["name"].

545
00:30:10,020 --> 00:30:12,710
And that curly brace
matches that curly brace.

546
00:30:12,710 --> 00:30:15,210
We've got our curly braces here.

547
00:30:15,210 --> 00:30:17,790
echo hello _GET["name"].

548
00:30:17,790 --> 00:30:19,912
Let's see if this works a little better.

549
00:30:19,912 --> 00:30:21,350
We're still running our server.

550
00:30:21,350 --> 00:30:23,910
Hello Jason.

551
00:30:23,910 --> 00:30:24,780
Hello Jason.

552
00:30:24,780 --> 00:30:25,810
And it worked this time.

553
00:30:25,810 --> 00:30:29,860
And so that's a proof
that you can indeed

554
00:30:29,860 --> 00:30:35,180
use the curly braces that you
know and love in PHP code in HTML.

555
00:30:35,180 --> 00:30:41,100
The PHP code provided to
you in pset 6-- pset 6--

556
00:30:41,100 --> 00:30:44,760
provides another way of
doing that same thing.

557
00:30:44,760 --> 00:30:49,220
>> So now we have the power.

558
00:30:49,220 --> 00:30:55,740
We have the functionality to implement
the PHP code that we saw in pset 6

559
00:30:55,740 --> 00:30:57,390
by ourselves, basically.

560
00:30:57,390 --> 00:31:01,350
Before I move on, what are some of the
questions that you have at this point?

561
00:31:01,350 --> 00:31:02,066
Yes [INAUDIBLE].

562
00:31:02,066 --> 00:31:06,512
>> AUDIENCE: So in the version in pset6,
when you run it, there's a space.

563
00:31:06,512 --> 00:31:09,330
And I can see where the space is
after the comma. [INAUDIBLE] start

564
00:31:09,330 --> 00:31:10,700
the open bracket.

565
00:31:10,700 --> 00:31:15,420
How do you incorporate the space in
the way you wrote your own codes?

566
00:31:15,420 --> 00:31:17,910
>> SPEAKER: That is a good question.

567
00:31:17,910 --> 00:31:21,650
And so let's figure that out.

568
00:31:21,650 --> 00:31:24,450
So that's a really good question
and one that I didn't consider.

569
00:31:24,450 --> 00:31:25,950
But let's do it together.

570
00:31:25,950 --> 00:31:30,280
>> So first of all, what
I'm doing with echo

571
00:31:30,280 --> 00:31:33,690
is when we just echo
hello, it outputs hello.

572
00:31:33,690 --> 00:31:41,310
If we echo now this get on a separate
line, let's examine what happens.

573
00:31:41,310 --> 00:31:43,740
So we click this.

574
00:31:43,740 --> 00:31:45,220
We keep saying, hi Jason.

575
00:31:45,220 --> 00:31:48,690
So again, we don't have this space.

576
00:31:48,690 --> 00:31:53,090
>> And that's because, in
PHP, when we have echo,

577
00:31:53,090 --> 00:31:55,820
no matter how many
spaces-- nope, not the V--

578
00:31:55,820 --> 00:32:01,770
no matter how many spaces we put in
here-- if we now load that up again,

579
00:32:01,770 --> 00:32:03,010
hi Jason.

580
00:32:03,010 --> 00:32:05,770
Yeah, see, all of those
spaces got eaten up.

581
00:32:05,770 --> 00:32:08,020
And that's something that
the echo function does.

582
00:32:08,020 --> 00:32:11,110
>> So to take care of
that space, and this is

583
00:32:11,110 --> 00:32:14,960
one of the reasons
why you don't use echo

584
00:32:14,960 --> 00:32:18,200
and you use htmlspecialchars instead.

585
00:32:18,200 --> 00:32:22,140
I'm curious what would
happen if we did this

586
00:32:22,140 --> 00:32:26,700
where we enclosed a space in a string.

587
00:32:26,700 --> 00:32:29,720
I'm honestly not sure what
will happen when I do this.

588
00:32:29,720 --> 00:32:30,790
>> So that's one way.

589
00:32:30,790 --> 00:32:32,210
That's one way to take care of it.

590
00:32:32,210 --> 00:32:34,840
If you wrap the space in
a string, then the space

591
00:32:34,840 --> 00:32:36,920
will be output nicely by echo.

592
00:32:36,920 --> 00:32:41,930
The safest thing to do is
to do htmlspecialchars.

593
00:32:41,930 --> 00:32:43,800
That's always the safe bet.

594
00:32:43,800 --> 00:32:47,050
But now we have a way to do
it with echo if necessary.

595
00:32:47,050 --> 00:32:50,700
And in a similar way, we can
echo new lines, all the sort

596
00:32:50,700 --> 00:32:53,550
of stuff you're familiar doing in PHP.

597
00:32:53,550 --> 00:32:57,460
>> Anyone else, what are any more
questions that other people have

598
00:32:57,460 --> 00:33:01,090
at this point about PHP?

599
00:33:01,090 --> 00:33:04,620
If people showed up a little late,
I'm happy to stay after a little bit

600
00:33:04,620 --> 00:33:06,420
and talk about some of the beginning.

601
00:33:06,420 --> 00:33:10,380
And it's also all livestreamed,
and archived, which is crazy.

602
00:33:10,380 --> 00:33:13,960
>> Anyway, so now let's do some
more advanced stuff with PHP.

603
00:33:13,960 --> 00:33:18,790
And one of the earliest things you
were introduced to in C was for loops.

604
00:33:18,790 --> 00:33:24,060
And PHP has a more powerful for
loop called the foreach loop.

605
00:33:24,060 --> 00:33:37,940
And it looks like this-- for each blank
as blank, curly brackets, do the thing.

606
00:33:37,940 --> 00:33:41,500
So this is basically a shorthand.

607
00:33:41,500 --> 00:33:45,380
>> See, the for loop as a
syntactical construction

608
00:33:45,380 --> 00:33:50,590
was devised in C and in assembly
language and things like.

609
00:33:50,590 --> 00:33:56,300
Devised in C, precisely, as a shorthand
for a lot of the types of loops

610
00:33:56,300 --> 00:33:57,750
that people would see.

611
00:33:57,750 --> 00:34:01,230
Like when you wrote a loop, there
was often an initialization step

612
00:34:01,230 --> 00:34:04,700
executed right at the beginning, a
condition where the loop would stop--

613
00:34:04,700 --> 00:34:07,030
and that's the feature
that's just in a while loop,

614
00:34:07,030 --> 00:34:10,040
or that a while has exactly
just that feature-- and then

615
00:34:10,040 --> 00:34:12,320
an incrementation step at the end.

616
00:34:12,320 --> 00:34:16,489
And so you'd often find yourself
writing code like the following.

617
00:34:16,489 --> 00:34:19,780
I'm going to erase some of this.

618
00:34:19,780 --> 00:34:23,850
>> But if we're iterating through
characters in an array,

619
00:34:23,850 --> 00:34:26,960
for instance, like we've
got an array of characters.

620
00:34:26,960 --> 00:34:29,400
Sorry to bring back C. I know,
you thought you were done.

621
00:34:29,400 --> 00:34:31,900
But it's only for the purpose
of learning PHP, I promise.

622
00:34:31,900 --> 00:34:38,880
So if you got a char str
of length 8, and let's

623
00:34:38,880 --> 00:34:46,760
say it says Hellooo
with a trailing null.

624
00:34:46,760 --> 00:34:48,270
Great, so that's our string.

625
00:34:48,270 --> 00:34:51,469
>> And then we had a for loop.

626
00:34:51,469 --> 00:34:53,730
We have int i equals 0.

627
00:34:53,730 --> 00:34:57,960

628
00:34:57,960 --> 00:35:09,110
And we want to exit when str
of i equals not equal to null,

629
00:35:09,110 --> 00:35:11,590
because we exit when it equals null.

630
00:35:11,590 --> 00:35:19,170
And then we do i++ at each
point in the for loop.

631
00:35:19,170 --> 00:35:30,480
Doing something with str of i.

632
00:35:30,480 --> 00:35:34,950
>> So the basic formula was,
we had this array that we

633
00:35:34,950 --> 00:35:37,910
wanted to treat as separate elements.

634
00:35:37,910 --> 00:35:45,170
But what we had to do is we had to
basically create a separate integer

635
00:35:45,170 --> 00:35:50,530
variable that was counting up every
time we went through the loop.

636
00:35:50,530 --> 00:35:55,240
And then we would have to then call
strstr[i] when what we really wanted to do

637
00:35:55,240 --> 00:35:57,280
is just go character
by character, right?

638
00:35:57,280 --> 00:36:00,185
We don't want to increment an
integer and then use that integer

639
00:36:00,185 --> 00:36:02,780
to access each character individually.

640
00:36:02,780 --> 00:36:04,410
We really want character by character.

641
00:36:04,410 --> 00:36:08,600
>> And so for each intelligently
calculates that for us.

642
00:36:08,600 --> 00:36:11,875
If we have an array, which
we can declare in PHP

643
00:36:11,875 --> 00:36:15,900
as just-- if we have a variable
called, let's call it array.

644
00:36:15,900 --> 00:36:19,840
The miracles of no typing, it's
just like any other variable.

645
00:36:19,840 --> 00:36:20,730
It's just an array.

646
00:36:20,730 --> 00:36:26,890
And we have a little [INAUDIBLE] like 1,
2, 3, just a sort of initialized array.

647
00:36:26,890 --> 00:36:29,680
It's OK, it doesn't like my foreach.

648
00:36:29,680 --> 00:36:33,120
>> But if we do foreach-- actually
I typed that a little wrong.

649
00:36:33,120 --> 00:36:34,840
There are two ways to do a foreach loop.

650
00:36:34,840 --> 00:36:37,400
There's the in syntax and the as syntax.

651
00:36:37,400 --> 00:36:40,580
And we're going to do
in syntax first, not as.

652
00:36:40,580 --> 00:36:41,780
That's my mistake.

653
00:36:41,780 --> 00:36:53,785
>> So foreach num in array, echo num.

654
00:36:53,785 --> 00:36:56,970

655
00:36:56,970 --> 00:36:59,500
And PHP is yelling at
me for some reason.

656
00:36:59,500 --> 00:37:03,520
It's finding an unexpected
in in something,

657
00:37:03,520 --> 00:37:05,820
which is a little bit of a bother.

658
00:37:05,820 --> 00:37:09,105
But we'll figure out
why that is in a moment.

659
00:37:09,105 --> 00:37:11,960

660
00:37:11,960 --> 00:37:13,610
So not like that.

661
00:37:13,610 --> 00:37:15,040
Let's try using the as.

662
00:37:15,040 --> 00:37:17,310
It prefers the as syntax is seems.

663
00:37:17,310 --> 00:37:22,550
So let's do foreach array as num.

664
00:37:22,550 --> 00:37:24,520
>> So a little explanation
of what just happened

665
00:37:24,520 --> 00:37:30,670
is the as syntax is saying-- well first,
let's look at what this prints out.

666
00:37:30,670 --> 00:37:32,260
So we open up our IDE.

667
00:37:32,260 --> 00:37:33,110
We go here.

668
00:37:33,110 --> 00:37:35,845
We say, Hello Jason.

669
00:37:35,845 --> 00:37:41,390
And it did 123, which were the contents
of the array that we created up top.

670
00:37:41,390 --> 00:37:45,500
>> So diving into this foreach loop,
we have a variable called array

671
00:37:45,500 --> 00:37:47,470
which is an array of three numbers.

672
00:37:47,470 --> 00:37:52,120
And then we are doing foreach
array as num, echo num.

673
00:37:52,120 --> 00:37:54,990
And that's more
intuitive than a for lop.

674
00:37:54,990 --> 00:38:02,380
We're saying, treating each of
the things in the array as num,

675
00:38:02,380 --> 00:38:05,180
I want you to give me num.

676
00:38:05,180 --> 00:38:06,640
And that's exactly what it's doing.

677
00:38:06,640 --> 00:38:12,000
>> PHP is calculating that
when you say foreach array,

678
00:38:12,000 --> 00:38:16,080
and you're dealing with an array, what
you're going to want to iterate over

679
00:38:16,080 --> 00:38:19,950
is the characters in that array,
is the ints in that array,

680
00:38:19,950 --> 00:38:21,920
is the elements in that array.

681
00:38:21,920 --> 00:38:26,110
And it's letting you store
those variables as num,

682
00:38:26,110 --> 00:38:29,360
and then just output num
right away rather than saying,

683
00:38:29,360 --> 00:38:34,090
I have a variable called i, and
then I want to output strstr[i].

684
00:38:34,090 --> 00:38:39,130
>> And so that allows us to do cool things.

685
00:38:39,130 --> 00:38:43,330
Like basically we don't have to create
these variables like i's and do all

686
00:38:43,330 --> 00:38:45,090
this incrementation stuff at the end.

687
00:38:45,090 --> 00:38:48,290
PHP takes care of all of that for you.

688
00:38:48,290 --> 00:38:54,470
>> So now let's talk about foreach as
it applies to our _GET dictionary.

689
00:38:54,470 --> 00:38:57,170
So we'll comment this out quickly.

690
00:38:57,170 --> 00:39:02,030
So we have our _GET array.

691
00:39:02,030 --> 00:39:04,361
We have this variable.

692
00:39:04,361 --> 00:39:05,610
And it's got some stuff in it.

693
00:39:05,610 --> 00:39:10,275
>> Right now, we only have one variable
being passed to it, which is name.

694
00:39:10,275 --> 00:39:13,420
But if we press Enter, now
we can have two variables.

695
00:39:13,420 --> 00:39:17,910
We can have name and age, for instance,
if we want to get the age and also

696
00:39:17,910 --> 00:39:20,960
the name of a person, funnily enough.

697
00:39:20,960 --> 00:39:25,690
>> So now _GET is going to be a
dictionary with two elements,

698
00:39:25,690 --> 00:39:27,980
with two key value pairs.

699
00:39:27,980 --> 00:39:33,490
And the first key-- I'm going to
write this one up on the board too.

700
00:39:33,490 --> 00:39:37,136
We have our dictionary is _GET.

701
00:39:37,136 --> 00:39:39,520
Sorry, it's is a little hard to see.

702
00:39:39,520 --> 00:39:46,690
But inside our dictionary we have
name, which is going to be something

703
00:39:46,690 --> 00:39:47,680
that we're given.

704
00:39:47,680 --> 00:39:53,040
And we'll have age, which is also
going to be something that we're given.

705
00:39:53,040 --> 00:39:56,020
And this is the entirety
of our dictionary.

706
00:39:56,020 --> 00:39:57,730
>> So it's got two elements in it.

707
00:39:57,730 --> 00:40:01,310
And so because foreach
loops are smart, we

708
00:40:01,310 --> 00:40:04,900
might think, and correctly
might think that foreach

709
00:40:04,900 --> 00:40:08,080
can iterate through this
dictionary, printing out

710
00:40:08,080 --> 00:40:10,850
the values given by name and age.

711
00:40:10,850 --> 00:40:14,510
>> So let's in fact do just that.

712
00:40:14,510 --> 00:40:17,520
Let's construct a foreach loop.

713
00:40:17,520 --> 00:40:23,351
And we're going to do for _GET as.

714
00:40:23,351 --> 00:40:24,850
And we're going to do the following.

715
00:40:24,850 --> 00:40:34,186
So let's see what happens if we type
just word, and then say echo word.

716
00:40:34,186 --> 00:40:40,540
We're also going to echo a new line
just to make it a little clearer,

717
00:40:40,540 --> 00:40:41,260
what's going on.

718
00:40:41,260 --> 00:40:42,890
>> So let's see.

719
00:40:42,890 --> 00:40:44,390
It's not giving me any errors.

720
00:40:44,390 --> 00:40:46,810
And we'll close this.

721
00:40:46,810 --> 00:40:51,020
On our website, you're going to be doing
a lot of that over the course of pset7.

722
00:40:51,020 --> 00:40:53,890
So we say my name is Sam.

723
00:40:53,890 --> 00:40:58,560
My age is 45.

724
00:40:58,560 --> 00:41:01,060
It's not.

725
00:41:01,060 --> 00:41:05,640
But it prints out, as expected, Sam 45.

726
00:41:05,640 --> 00:41:08,930
>> And so you'll notice that
what foreach loop did-- here,

727
00:41:08,930 --> 00:41:12,360
let's go back to that so it's up
on the board-- we get _GET as word.

728
00:41:12,360 --> 00:41:15,130
And there were four things in _GET.

729
00:41:15,130 --> 00:41:17,410
But it only printed out two things.

730
00:41:17,410 --> 00:41:21,290
foreach, being its intelligence self,
assumed that what we really wanted

731
00:41:21,290 --> 00:41:24,100
was the values, not the keys.

732
00:41:24,100 --> 00:41:27,800
>> But there is a way that we could print
out the keys as well, if we wanted to.

733
00:41:27,800 --> 00:41:30,810
If we wanted to also know what
these variables were called,

734
00:41:30,810 --> 00:41:33,540
there's a way that we
can access this as well.

735
00:41:33,540 --> 00:41:36,840
And the way to sort of do that,
so we can say, lets really

736
00:41:36,840 --> 00:41:39,485
split it into key value pairs.

737
00:41:39,485 --> 00:41:42,370

738
00:41:42,370 --> 00:41:47,580
So let's see what happens now.

739
00:41:47,580 --> 00:41:50,550
>> So we have key.

740
00:41:50,550 --> 00:41:52,290
We have value.

741
00:41:52,290 --> 00:41:56,650
We have another new
line for readability.

742
00:41:56,650 --> 00:42:00,540
And let's see what happens
when we do this now.

743
00:42:00,540 --> 00:42:04,950

744
00:42:04,950 --> 00:42:06,720
I don't know how old Jason is.

745
00:42:06,720 --> 00:42:09,180
Jason's 15.

746
00:42:09,180 --> 00:42:11,650
So we have name Jason, age 15.

747
00:42:11,650 --> 00:42:15,830
So we were able to access the key
and value pairs of this dictionary

748
00:42:15,830 --> 00:42:18,590
just by saying as key points to value.

749
00:42:18,590 --> 00:42:23,350
And that's a foreach syntactic
sugar bit that allows

750
00:42:23,350 --> 00:42:25,960
you to access things in the dictionary.

751
00:42:25,960 --> 00:42:31,190
>> So hopefully this sort of emphasizes
the power of the foreach loop.

752
00:42:31,190 --> 00:42:35,690
You can pretty much throw
anything that seems iterable,

753
00:42:35,690 --> 00:42:38,922
like anything that has multiple
elements like an array,

754
00:42:38,922 --> 00:42:41,880
like a dictionary-- those are two
primary things you'll be working with

755
00:42:41,880 --> 00:42:45,630
both in life and in pset 7.

756
00:42:45,630 --> 00:42:49,350
So you can throw that stuff
at it, and it will figure out

757
00:42:49,350 --> 00:42:51,030
what you want to do with it.

758
00:42:51,030 --> 00:42:54,250
It'll say, OK, I'm going to get
these things from the data that

759
00:42:54,250 --> 00:42:55,680
was passed to me.

760
00:42:55,680 --> 00:43:02,470
And that's something that you're
going to be using a lot of in pset 7.

761
00:43:02,470 --> 00:43:08,550
>> I'm going to quick scroll
down just to see where I'm at.

762
00:43:08,550 --> 00:43:11,410

763
00:43:11,410 --> 00:43:13,070
Do people have questions at this point?

764
00:43:13,070 --> 00:43:13,778
Questions at all?

765
00:43:13,778 --> 00:43:14,400
Yes?

766
00:43:14,400 --> 00:43:18,320
>> AUDIENCE: So with the key and value,
you could name it anything else

767
00:43:18,320 --> 00:43:20,507
and it would still work?

768
00:43:20,507 --> 00:43:21,090
SPEAKER: Oops.

769
00:43:21,090 --> 00:43:22,820
Wow, I totally deleted the whole line.

770
00:43:22,820 --> 00:43:23,380
Great work.

771
00:43:23,380 --> 00:43:26,502
So a, a.

772
00:43:26,502 --> 00:43:30,109
Key and value is just a convention.

773
00:43:30,109 --> 00:43:30,650
It's helpful.

774
00:43:30,650 --> 00:43:34,010
You would get some design
points, maybe some style points

775
00:43:34,010 --> 00:43:36,970
for doing that because it
really conveys the intention.

776
00:43:36,970 --> 00:43:39,650
But we say a and yarp.

777
00:43:39,650 --> 00:43:42,476
>> AUDIENCE: You don't have to
change anything in the HTML file

778
00:43:42,476 --> 00:43:43,607
in order to reflect that?

779
00:43:43,607 --> 00:43:44,440
SPEAKER: Not at all.

780
00:43:44,440 --> 00:43:47,260
AUDIENCE: And it just knows that
because of the equals greater than--

781
00:43:47,260 --> 00:43:47,801
SPEAKER: Yes.

782
00:43:47,801 --> 00:43:49,489
AUDIENCE: --that indicator that that's--

783
00:43:49,489 --> 00:43:50,030
SPEAKER: Yes.

784
00:43:50,030 --> 00:43:52,260
That is a foreach syntax, but yes.

785
00:43:52,260 --> 00:43:53,720
>> AUDIENCE: There are not types.

786
00:43:53,720 --> 00:43:57,230
So what if you wanted
age to only be a number?

787
00:43:57,230 --> 00:43:59,510
Is there a way to do that?

788
00:43:59,510 --> 00:44:04,550
>> SPEAKER: There are ways to check if
variables conform to certain types.

789
00:44:04,550 --> 00:44:08,482
So PHP asks a little more from
you because there are no types in.

790
00:44:08,482 --> 00:44:09,440
Some ways it asks less.

791
00:44:09,440 --> 00:44:11,070
In some ways it asks more.

792
00:44:11,070 --> 00:44:13,320
Because if you have just
something in a variable,

793
00:44:13,320 --> 00:44:14,960
you have no idea what type it is.

794
00:44:14,960 --> 00:44:19,310
But if you are smart about the variables
that you assign types to and make sure

795
00:44:19,310 --> 00:44:22,750
that functions only return-- you
want functions to only return

796
00:44:22,750 --> 00:44:26,210
one type of value so
that you can basically

797
00:44:26,210 --> 00:44:31,090
expect that the variable you get back
from a function will be of the type

798
00:44:31,090 --> 00:44:32,780
that you think it will be, basically.

799
00:44:32,780 --> 00:44:36,550
>> But there are some methods
by which you can check.

800
00:44:36,550 --> 00:44:39,801
I don't remember them
off the top of my head.

801
00:44:39,801 --> 00:44:43,300
I'm waiting for it to turn blue.

802
00:44:43,300 --> 00:44:45,560
isint?

803
00:44:45,560 --> 00:44:48,070
isstr?

804
00:44:48,070 --> 00:44:52,000
There are methods
built into PHP that can

805
00:44:52,000 --> 00:44:54,440
check the type of variables for you.

806
00:44:54,440 --> 00:44:58,250
But if you assign variables
smartly, you should not

807
00:44:58,250 --> 00:45:01,330
have to do that too much in pset 7.

808
00:45:01,330 --> 00:45:02,780
But those methods do exist.

809
00:45:02,780 --> 00:45:06,704
And that's something that
is in the language itself.

810
00:45:06,704 --> 00:45:08,370
And I don't remember the precise syntax.

811
00:45:08,370 --> 00:45:09,930
We could even look it up.

812
00:45:09,930 --> 00:45:11,974
But time is of the essence.

813
00:45:11,974 --> 00:45:13,890
have Does anyone else
have any more questions?

814
00:45:13,890 --> 00:45:14,660
Yes.

815
00:45:14,660 --> 00:45:15,951
>> AUDIENCE: I have just one more.

816
00:45:15,951 --> 00:45:19,050
So you mentioned the GET method, but
you didn't mention the POST method.

817
00:45:19,050 --> 00:45:20,500
Are we coming back to that?

818
00:45:20,500 --> 00:45:21,540
>> SPEAKER: Yes, we will
be coming back to that.

819
00:45:21,540 --> 00:45:24,840
That's exactly what I was looking
at my phone, which now fell asleep,

820
00:45:24,840 --> 00:45:26,960
but I'll find it.

821
00:45:26,960 --> 00:45:30,680
Just making sure we hit
all of the PHP notes.

822
00:45:30,680 --> 00:45:35,640
Yep, there's no debugging version.

823
00:45:35,640 --> 00:45:41,940
Yes, we have a few more things that
we want to do now at this point.

824
00:45:41,940 --> 00:45:45,980
>> So talking about POST,
which you mentioned,

825
00:45:45,980 --> 00:45:49,630
the only difference
between GET and POST is

826
00:45:49,630 --> 00:45:53,150
that remember when we looked
at this URL and we saw, oh,

827
00:45:53,150 --> 00:45:58,270
name equals a and age equals yarp
are right in the URL there for us.

828
00:45:58,270 --> 00:46:03,300
POST is a little more secretive
with its passing of information.

829
00:46:03,300 --> 00:46:08,090
>> So if you didn't want a user
to know, for instance, you

830
00:46:08,090 --> 00:46:11,160
didn't want the username
and password of the person

831
00:46:11,160 --> 00:46:15,080
currently logged in to be displayed in
the URL, which is a reasonable thing

832
00:46:15,080 --> 00:46:17,770
to not want in the URL,
because someone can see it.

833
00:46:17,770 --> 00:46:21,520
If they link someone to a page, you
don't want their URL plastered there,

834
00:46:21,520 --> 00:46:27,850
because that would allow people to login
just with the pasting of a URL instead

835
00:46:27,850 --> 00:46:29,670
of actually filling out a form.

836
00:46:29,670 --> 00:46:31,710
POST is a little bit more secretive.

837
00:46:31,710 --> 00:46:34,150
>> And the only things that
we'll have to change

838
00:46:34,150 --> 00:46:38,550
are this method, change
from get to post.

839
00:46:38,550 --> 00:46:42,367
And then inside the HTTP, instead
of accessing the array _GET,

840
00:46:42,367 --> 00:46:43,950
we're going to access the array _POST.

841
00:46:43,950 --> 00:46:48,600
>> And we'll notice that, if
we open this back up again,

842
00:46:48,600 --> 00:46:51,910
Jason slowly declines in age.

843
00:46:51,910 --> 00:46:53,230
name Jason, age 14.

844
00:46:53,230 --> 00:46:54,280
The same stuff pops up.

845
00:46:54,280 --> 00:46:57,190
But we go to the URL and
those variables aren't there.

846
00:46:57,190 --> 00:47:00,540
>> And the way that POST
passes-- so remember

847
00:47:00,540 --> 00:47:02,750
how to look at the source of a page.

848
00:47:02,750 --> 00:47:04,570
We go to the network.

849
00:47:04,570 --> 00:47:06,920
We refresh.

850
00:47:06,920 --> 00:47:10,690
And this is another thing that
POST will give you warnings about.

851
00:47:10,690 --> 00:47:15,050
You might have seen a box, a text
box like this in your browser.

852
00:47:15,050 --> 00:47:18,170
Are you sure you want
to send a form again?

853
00:47:18,170 --> 00:47:21,170
POST is what 's sending these forms.

854
00:47:21,170 --> 00:47:24,680
>> Because basically if you sent your
credit card information to someone,

855
00:47:24,680 --> 00:47:26,350
that's not going to show up in the URL.

856
00:47:26,350 --> 00:47:28,180
That's going to be a POST request.

857
00:47:28,180 --> 00:47:32,905
So when you refresh the page,
it's resending that post request.

858
00:47:32,905 --> 00:47:35,530
So now we do want to send the
form again because it's not going

859
00:47:35,530 --> 00:47:37,340
to create any duplicate purchases.

860
00:47:37,340 --> 00:47:41,160
>> And we'll notice that down here,
the method we're using is POST.

861
00:47:41,160 --> 00:47:43,065
And it did indeed transfer bytes.

862
00:47:43,065 --> 00:47:45,460
It transferred 401 of them.

863
00:47:45,460 --> 00:47:47,190
Program's pretty tiny.

864
00:47:47,190 --> 00:47:51,600
But there's nowhere that we can see
the values that are being passed.

865
00:47:51,600 --> 00:47:59,540
The web pages themselves can see,
but we as users are not able to see,

866
00:47:59,540 --> 00:48:01,650
unless you're a hacker.

867
00:48:01,650 --> 00:48:05,340
If you're a good hacker, you can look.

868
00:48:05,340 --> 00:48:09,360
>> If you know the basic
format of the HTML,

869
00:48:09,360 --> 00:48:11,790
the values will make
themselves known in the pages.

870
00:48:11,790 --> 00:48:13,160
You'll be able to see.

871
00:48:13,160 --> 00:48:16,720
The values will be there, they're
just a little less obvious for you

872
00:48:16,720 --> 00:48:19,522
to access, basically.

873
00:48:19,522 --> 00:48:23,620
>> Do we have any more
questions about GET, POST

874
00:48:23,620 --> 00:48:26,800
before-- what we're going to do next
is actually look at some of the code

875
00:48:26,800 --> 00:48:30,837
that you're giving in pset 7, talk about
how it uses some of these concepts,

876
00:48:30,837 --> 00:48:32,670
and talk about the
things that you are going

877
00:48:32,670 --> 00:48:35,090
to have to do a little bit in pset 7.

878
00:48:35,090 --> 00:48:36,760
Any more questions before that?

879
00:48:36,760 --> 00:48:38,047
More questions you guys have?

880
00:48:38,047 --> 00:48:41,250

881
00:48:41,250 --> 00:48:41,840
Great.

882
00:48:41,840 --> 00:48:45,370
>> All right, let's look
a little bit at pset 7,

883
00:48:45,370 --> 00:48:49,530
no doubt what you are
all most excited about.

884
00:48:49,530 --> 00:48:52,126

885
00:48:52,126 --> 00:48:54,750
I mean, this is something that
David goes through a little bit.

886
00:48:54,750 --> 00:49:00,890
But we'll have three directories at the
top, as well as a configuration file.

887
00:49:00,890 --> 00:49:04,650
That's for databases, which we'll
talk about in about five minutes.

888
00:49:04,650 --> 00:49:07,220
Includes, you never need
to look in this directory

889
00:49:07,220 --> 00:49:12,480
if you don't want to but it's nice to
know there are all sorts of helpers.

890
00:49:12,480 --> 00:49:14,210
Helpers is like helpful functions.

891
00:49:14,210 --> 00:49:18,120
And then we have config,
which sets some stuff up.

892
00:49:18,120 --> 00:49:24,590
>> There are some functions that CS50 has
written that are in helper and config.

893
00:49:24,590 --> 00:49:27,250
And some of the PHP that
already exits in files

894
00:49:27,250 --> 00:49:30,880
will do a lot of the more sort
of obtuse leg work for you.

895
00:49:30,880 --> 00:49:35,250
Like if we go into public
login.php, which is what

896
00:49:35,250 --> 00:49:38,350
shows up right when you go into pset 7.

897
00:49:38,350 --> 00:49:40,580
We'll see that there's
this require statement.

898
00:49:40,580 --> 00:49:43,420
And that sort of like a
sharp include, hashtag

899
00:49:43,420 --> 00:49:46,850
include if you're of a newer generation.

900
00:49:46,850 --> 00:49:49,740
But this basically
says that I need access

901
00:49:49,740 --> 00:49:52,260
to all the functions in config.php.

902
00:49:52,260 --> 00:49:55,290
And you could have a require
for all sorts of other things.

903
00:49:55,290 --> 00:49:59,670
>> config actually requires helpers.

904
00:49:59,670 --> 00:50:02,490
So whenever you require
config, you're also

905
00:50:02,490 --> 00:50:05,660
including or requiring helpers as well.

906
00:50:05,660 --> 00:50:09,590
So that gives you access to all the
cool functions that we're going to use,

907
00:50:09,590 --> 00:50:10,420
things like render.

908
00:50:10,420 --> 00:50:13,490
I'm actually going to ease
this down a little bit.

909
00:50:13,490 --> 00:50:16,280
So the function then we're
going to walk through

910
00:50:16,280 --> 00:50:22,380
just before we move on to SQL a little
bit is the login.php function, just

911
00:50:22,380 --> 00:50:26,586
because it uses some of the topics
that we just talked about in PHP.

912
00:50:26,586 --> 00:50:30,840
>> You see the first thing is if $_SERVER.

913
00:50:30,840 --> 00:50:34,500
This is another global variable that
you're going to be dealing with.

914
00:50:34,500 --> 00:50:38,460
It's like _GET and _POST, but what
server contains is this can let you

915
00:50:38,460 --> 00:50:42,730
know if the request method
was a GET or a POST.

916
00:50:42,730 --> 00:50:47,250
Like previously what we were doing
is just in our code that we wrote,

917
00:50:47,250 --> 00:50:51,880
we were just changing it to be GET and
POST depending on what the HTML has.

918
00:50:51,880 --> 00:50:55,120
But there are pages that can be
accessed with both types of requests.

919
00:50:55,120 --> 00:50:57,410
And you might want to do
different things depending

920
00:50:57,410 --> 00:50:59,740
on the type of request,
just like login does.

921
00:50:59,740 --> 00:51:04,400
>> So you can check that request
method through accessing keys,

922
00:51:04,400 --> 00:51:08,630
through using a key and getting the
value of something in the dictionary

923
00:51:08,630 --> 00:51:10,260
_SERVER.

924
00:51:10,260 --> 00:51:13,800
So that's another global
variable like _GET and _POST.

925
00:51:13,800 --> 00:51:16,990
>> If it's GET, we want to
render the login form.

926
00:51:16,990 --> 00:51:21,920
Render is a function that basically
just puts up the appropriate HTML

927
00:51:21,920 --> 00:51:24,500
and passes it some parameters.

928
00:51:24,500 --> 00:51:28,740
This title is a parameter that's
used in displaying, oddly enough,

929
00:51:28,740 --> 00:51:32,670
the title of the page in
question, the thing up here,

930
00:51:32,670 --> 00:51:34,850
say or hello in our previous example.

931
00:51:34,850 --> 00:51:36,100
Now we have a different thing.

932
00:51:36,100 --> 00:51:38,570
Else if it's POST, we
do some other stuff.

933
00:51:38,570 --> 00:51:40,790
We're using that empty method.

934
00:51:40,790 --> 00:51:42,750
It's not exist, it's empty.

935
00:51:42,750 --> 00:51:45,440
And we saw before, PHP
has a fair amount of built

936
00:51:45,440 --> 00:51:52,370
in methods that David will-- if there
are methods that are useful to you,

937
00:51:52,370 --> 00:51:55,560
they will be alerted to you
in the walk through that David

938
00:51:55,560 --> 00:51:59,770
gives at the beginning overview,
and also Zamyla's helpful bits.

939
00:51:59,770 --> 00:52:01,040
She's back everyone.

940
00:52:01,040 --> 00:52:03,100
We can all rejoice.

941
00:52:03,100 --> 00:52:06,530
apologize is an aptly named function
that just basically prints out

942
00:52:06,530 --> 00:52:10,130
some error messages,
because CS50 is very polite.

943
00:52:10,130 --> 00:52:14,770
>> And now this, this is a
tricky bit because this

944
00:52:14,770 --> 00:52:16,697
is where we're querying the database.

945
00:52:16,697 --> 00:52:18,280
Now we haven't talked about databases.

946
00:52:18,280 --> 00:52:22,220
And we're going to in the next
five minutes or so, maximum.

947
00:52:22,220 --> 00:52:24,980
But this is a function
that CS50 has written

948
00:52:24,980 --> 00:52:38,050
to get a table basically from a database
that we're working with in pset 7.

949
00:52:38,050 --> 00:52:40,860
I'm really bad with my
zero indexing today.

950
00:52:40,860 --> 00:52:42,060
But yes, it is 7.

951
00:52:42,060 --> 00:52:46,340
>> So query it's going to return an
array, basically is the key bit.

952
00:52:46,340 --> 00:52:54,130
And because these things don't have
typing, so rows is an array of arrays.

953
00:52:54,130 --> 00:52:59,480
Because when we're thinking about
a table, what we're going to do

954
00:52:59,480 --> 00:53:04,830
is, as you learned in psets
like the game of 15, anyway

955
00:53:04,830 --> 00:53:06,990
where you had to use a
double array, we basically

956
00:53:06,990 --> 00:53:15,210
have array of other
arrays makes a table.

957
00:53:15,210 --> 00:53:18,150
And you've got rows and columns.

958
00:53:18,150 --> 00:53:24,450
And then you can access them like
[0] [1], you get the [0] [1].

959
00:53:24,450 --> 00:53:26,900
Basic stuff like that.

960
00:53:26,900 --> 00:53:29,380
>> So what we're doing
here in this function,

961
00:53:29,380 --> 00:53:35,070
we're asking the database
if the user that's

962
00:53:35,070 --> 00:53:40,200
trying to login, that will be
sent through the POST method.

963
00:53:40,200 --> 00:53:43,950
We'll see we're getting
the username from _POST.

964
00:53:43,950 --> 00:53:46,900
They'll have sent, the user
or you, will send a value

965
00:53:46,900 --> 00:53:50,750
through a form through POST because
it's username and password stuff.

966
00:53:50,750 --> 00:53:54,830
We're checking the username
to see, is this in the table?

967
00:53:54,830 --> 00:53:58,070
Because if a user is logging
in, then their username

968
00:53:58,070 --> 00:54:03,320
should be stored in the table of
users that exist for this site.

969
00:54:03,320 --> 00:54:09,360
So basically if the
user is in the database,

970
00:54:09,360 --> 00:54:16,400
query is going to return
that row, which is an array.

971
00:54:16,400 --> 00:54:24,560
>> But the tricky part is that if even if
the double array is only of one row,

972
00:54:24,560 --> 00:54:31,900
even if it's a one row array--
like you've got basically--

973
00:54:31,900 --> 00:54:36,900
if you've got a size one array
that's holding another array,

974
00:54:36,900 --> 00:54:38,940
you're really dealing with one column.

975
00:54:38,940 --> 00:54:41,420
But it's still treated
like a double array.

976
00:54:41,420 --> 00:54:44,560
>> And this is where it can sometimes get
tricky, because we've got rows here.

977
00:54:44,560 --> 00:54:46,440
Our variable is rows.

978
00:54:46,440 --> 00:54:48,590
And then we're creating
a new variable called row

979
00:54:48,590 --> 00:54:51,450
and setting it equal to
the first row of rows.

980
00:54:51,450 --> 00:54:55,150
And you'll notice that comment
says it's the first and only row.

981
00:54:55,150 --> 00:54:57,080
>> So this is the tricky
part where now functions

982
00:54:57,080 --> 00:54:59,660
can return arrays very easily.

983
00:54:59,660 --> 00:55:01,270
There's not mallocs.

984
00:55:01,270 --> 00:55:02,280
You won't see mallocs.

985
00:55:02,280 --> 00:55:03,940
So you won't see seg faults.

986
00:55:03,940 --> 00:55:08,380
But functions will still be passing
around arrays and data in groups.

987
00:55:08,380 --> 00:55:12,250
And you have to be wary of what
exactly your functions will return.

988
00:55:12,250 --> 00:55:15,160
And even if it's one
column like this, query

989
00:55:15,160 --> 00:55:17,520
is still going to return a double array.

990
00:55:17,520 --> 00:55:21,390
So to access that column-- or you
can think of all of this as inverted

991
00:55:21,390 --> 00:55:22,870
since we're talking about rows.

992
00:55:22,870 --> 00:55:26,810
But to access that one row,
you can't just say rows.

993
00:55:26,810 --> 00:55:31,540
Even though it is one row, you have to
do rowsrows[0] to sort of eliminate this

994
00:55:31,540 --> 00:55:37,360
outer bit of the array and
have just your one row.

995
00:55:37,360 --> 00:55:38,342
>> Do some other things.

996
00:55:38,342 --> 00:55:40,050
There's a function
called password_verify

997
00:55:40,050 --> 00:55:42,980
that verifies the
password that was POSTed.

998
00:55:42,980 --> 00:55:48,500
And then we see another global
variable here, _SESSION.

999
00:55:48,500 --> 00:55:51,340
Basically session id
is how you keep track

1000
00:55:51,340 --> 00:55:53,990
of if someone is logged in or not.

1001
00:55:53,990 --> 00:55:58,590
So right now with login.php,
we're logging a user in.

1002
00:55:58,590 --> 00:56:01,920
So what we want to do is we want to
say the session id is equal to the row

1003
00:56:01,920 --> 00:56:05,890
id, which just makes sense because
each row will have a different id

1004
00:56:05,890 --> 00:56:07,239
number as part of the table.

1005
00:56:07,239 --> 00:56:09,280
We'll get into SQL in a
second, so if any of this

1006
00:56:09,280 --> 00:56:13,500
seems a little bit like blah,
then all will be cleared up.

1007
00:56:13,500 --> 00:56:18,450
But we're going to set the id equal to
the proper thing, logging the user in.

1008
00:56:18,450 --> 00:56:20,530
Apologize if anything goes wrong.

1009
00:56:20,530 --> 00:56:27,600
And that is logins purpose in
life as Professor Malan would say.

1010
00:56:27,600 --> 00:56:29,130
>> So that was login.php.

1011
00:56:29,130 --> 00:56:33,750
And a lot of the PHP code you write
in pset 7, they'll be a little bit.

1012
00:56:33,750 --> 00:56:36,470
Don't forget to chmod to
the proper permissions.

1013
00:56:36,470 --> 00:56:40,180
There will be a little bit about
that in the beginning of the spec.

1014
00:56:40,180 --> 00:56:46,382
>> But the PHP that you're
writing is going to be

1015
00:56:46,382 --> 00:56:47,840
doing stuff that's similar to this.

1016
00:56:47,840 --> 00:56:49,715
You're going to be
accessing some things that

1017
00:56:49,715 --> 00:56:52,760
are given to you in the
global variables of PHP that

1018
00:56:52,760 --> 00:56:56,105
are dealing with the current
logged in user, whether there

1019
00:56:56,105 --> 00:57:00,460
have been requests sent to this
page, different things like that.

1020
00:57:00,460 --> 00:57:05,790
And it will also be potentially
iterating through rows of this thing.

1021
00:57:05,790 --> 00:57:09,010
>> In a different function, query
does return this double array.

1022
00:57:09,010 --> 00:57:11,450
And if there are more
than one rows in it,

1023
00:57:11,450 --> 00:57:15,080
if there are-- yes, if there
are more than one rows in it,

1024
00:57:15,080 --> 00:57:16,870
then it will be a table.

1025
00:57:16,870 --> 00:57:20,500
And you might want to iterate
through the rows of this array using

1026
00:57:20,500 --> 00:57:22,860
the foreach loop that we described.

1027
00:57:22,860 --> 00:57:30,270
>> So if you do foreach on a double
array, what will the word-- here,

1028
00:57:30,270 --> 00:57:31,909
I'll actually write it.

1029
00:57:31,909 --> 00:57:32,950
I'll write it quick here.

1030
00:57:32,950 --> 00:57:44,280
>> If we have a foreach of rows
as row, what's the type of row?

1031
00:57:44,280 --> 00:57:45,390
Does anyone know?

1032
00:57:45,390 --> 00:57:54,000

1033
00:57:54,000 --> 00:57:54,500
You got it?

1034
00:57:54,500 --> 00:57:57,110
So rows is a double array.

1035
00:57:57,110 --> 00:58:02,810
So what is foreach going to infer
that we want from this double array

1036
00:58:02,810 --> 00:58:04,280
if we're iterating over it?

1037
00:58:04,280 --> 00:58:07,170

1038
00:58:07,170 --> 00:58:10,770
We can basically assume that
it's going to be either elements,

1039
00:58:10,770 --> 00:58:14,970
or rows, or columns, basically.

1040
00:58:14,970 --> 00:58:18,740
And so rows and columns we
can treat as the same thing.

1041
00:58:18,740 --> 00:58:23,880
>> Basically what the foreach loop is going
to do is it's going to return rows.

1042
00:58:23,880 --> 00:58:28,500
row is going to be of type row,
whereas rows is a double array.

1043
00:58:28,500 --> 00:58:32,290
So if you give foreach
a double array, it's

1044
00:58:32,290 --> 00:58:35,830
not going to iterate
more than one level deep.

1045
00:58:35,830 --> 00:58:44,464
Which is basically to say if there
are eight cells in this table-- 1,2,

1046
00:58:44,464 --> 00:58:48,110
3 4, 5, 6, 7, 8-- the
foreach loop is not

1047
00:58:48,110 --> 00:58:51,880
going to go through each of these cells.

1048
00:58:51,880 --> 00:58:56,390
What the foreach loop will do
was it will go through this row,

1049
00:58:56,390 --> 00:58:57,870
give you this whole row.

1050
00:58:57,870 --> 00:58:59,410
And then it'll go through that row.

1051
00:58:59,410 --> 00:59:01,850
>> So it only iterates one level deep.

1052
00:59:01,850 --> 00:59:05,310
If you add a nested
foreach loop, then you

1053
00:59:05,310 --> 00:59:16,280
can treat each row returned from
rows, you do foreach row as element,

1054
00:59:16,280 --> 00:59:17,640
let's say.

1055
00:59:17,640 --> 00:59:22,750
And then you could echo the element.

1056
00:59:22,750 --> 00:59:24,930
So that's a brief
little refresher on how

1057
00:59:24,930 --> 00:59:30,220
you might be using foreach
loops in the context of query.

1058
00:59:30,220 --> 00:59:32,840
>> Are there any questions on PHP?

1059
00:59:32,840 --> 00:59:36,520
Anything at all before we
move on to talking about SQL

1060
00:59:36,520 --> 00:59:37,820
and the fun of database?

1061
00:59:37,820 --> 00:59:41,480

1062
00:59:41,480 --> 00:59:42,110
Feeling good?

1063
00:59:42,110 --> 00:59:42,750
Feeling good.

1064
00:59:42,750 --> 00:59:43,470
All right.

1065
00:59:43,470 --> 00:59:49,130
>> Let's move on back to the
PowerPoint, which you probably miss.

1066
00:59:49,130 --> 00:59:51,800
SQL, yay.

1067
00:59:51,800 --> 00:59:57,900
People who are in my section typically
will know that subheadings of acronyms

1068
00:59:57,900 --> 01:00:01,220
are always just the first words
I think of that match that

1069
01:00:01,220 --> 01:00:02,690
algorithm-- that acronym.

1070
01:00:02,690 --> 01:00:04,090
It's not an algorithm.

1071
01:00:04,090 --> 01:00:08,050
>> So SQL is a database.

1072
01:00:08,050 --> 01:00:11,060
It's a language that
works with databases.

1073
01:00:11,060 --> 01:00:14,440
And all databases are is
tables, at least in the way

1074
01:00:14,440 --> 01:00:17,220
that SQL represents them.

1075
01:00:17,220 --> 01:00:23,610
>> Another way to think about databases is
databases are a set of keys and values

1076
01:00:23,610 --> 01:00:24,110
basically.

1077
01:00:24,110 --> 01:00:29,530
You can think about a database as
a dictionary and also as a table.

1078
01:00:29,530 --> 01:00:34,300
Basically it's a way to associate
different data with other data,

1079
01:00:34,300 --> 01:00:36,270
often through rows and columns.

1080
01:00:36,270 --> 01:00:38,470
And that's the way
that's SQL works best.

1081
01:00:38,470 --> 01:00:40,880
>> So this is one example of a table.

1082
01:00:40,880 --> 01:00:44,610
I've got a few examples of
people in my section, which

1083
01:00:44,610 --> 01:00:45,970
I didn't have time to change.

1084
01:00:45,970 --> 01:00:52,020
But we've got things like ID,
name, superpower, and hometown.

1085
01:00:52,020 --> 01:00:54,100
I don't know where anyone's
from in my section,

1086
01:00:54,100 --> 01:00:56,266
so I'm just going to assume
everyone's from New York

1087
01:00:56,266 --> 01:00:59,370
City because I have a high statistical
likelihood of being correct.

1088
01:00:59,370 --> 01:01:04,200
>> SQL will automatically take
care of the ID column for you.

1089
01:01:04,200 --> 01:01:07,560
If you insert a new row
into a SQL database,

1090
01:01:07,560 --> 01:01:09,700
it will increment that
ID number and just

1091
01:01:09,700 --> 01:01:14,890
basically stick like five names,
superpower, hometown, whoever

1092
01:01:14,890 --> 01:01:16,430
onto the end of that table.

1093
01:01:16,430 --> 01:01:19,160
So ID is a column you'll
never have to worry about.

1094
01:01:19,160 --> 01:01:22,770
But, like in the case
of login.php, when we

1095
01:01:22,770 --> 01:01:26,610
were getting the session ID
from a table and just using ID,

1096
01:01:26,610 --> 01:01:30,320
ID is a way to uniquely identify
an element of a database.

1097
01:01:30,320 --> 01:01:34,980
>> So if we had two Sams, both of
which taught CS50, and both of who

1098
01:01:34,980 --> 01:01:39,370
were from Milwaukee, those would
still have distinct ID numbers

1099
01:01:39,370 --> 01:01:43,420
and thus be distinct in
the context of the table.

1100
01:01:43,420 --> 01:01:48,700
So this is what SQL is dealing
with, working with in the back end.

1101
01:01:48,700 --> 01:01:54,160
>> Now these are the four commands
that you'll need to work with SQL.

1102
01:01:54,160 --> 01:01:56,390
And I threw them all up on one slide.

1103
01:01:56,390 --> 01:01:59,530
But we're going to go through
them all individually.

1104
01:01:59,530 --> 01:02:03,300
>> The first command is UPDATE,
which does what you might expect.

1105
01:02:03,300 --> 01:02:07,240
Say you have some data in
the table that's out of date.

1106
01:02:07,240 --> 01:02:09,470
Like if you're keeping
track of people's names

1107
01:02:09,470 --> 01:02:13,350
and ages, if someone's
age increases, then

1108
01:02:13,350 --> 01:02:18,590
you're going to want to go in and
update just that person's age.

1109
01:02:18,590 --> 01:02:21,902
For an example that works
with our first table--

1110
01:02:21,902 --> 01:02:24,610
don't worry about writing all of
these commands at the same time.

1111
01:02:24,610 --> 01:02:27,640
But if you've got update down,
that'll be good for this part,

1112
01:02:27,640 --> 01:02:29,790
because we're going to
go back to the table.

1113
01:02:29,790 --> 01:02:33,920
>> So if we go back to the table,
let's say something that happened

1114
01:02:33,920 --> 01:02:38,480
was there was an earthquake or
a fault line that split directly

1115
01:02:38,480 --> 01:02:39,920
through New York City.

1116
01:02:39,920 --> 01:02:45,130
And we wanted to update everyone
who lived in New York City.

1117
01:02:45,130 --> 01:02:49,670
They all had to move to Pennsylvania.

1118
01:02:49,670 --> 01:02:51,130
That's not a hometown.

1119
01:02:51,130 --> 01:02:53,180
They all had to move to New Haven.

1120
01:02:53,180 --> 01:02:54,030
There we go.

1121
01:02:54,030 --> 01:02:57,630
So everyone in New York
moves to New Haven.

1122
01:02:57,630 --> 01:03:01,300
>> And so that's something that's
editing three rows in this table.

1123
01:03:01,300 --> 01:03:04,716
But in SQL, you can do
that in just one statement.

1124
01:03:04,716 --> 01:03:05,715
So we go back to UPDATE.

1125
01:03:05,715 --> 01:03:09,670
Let me quick erase this board again.

1126
01:03:09,670 --> 01:03:14,570
When we're talking about
updating, there are

1127
01:03:14,570 --> 01:03:17,640
a few parts of the syntax that are key.

1128
01:03:17,640 --> 01:03:19,770
Well, all of the syntax is key.

1129
01:03:19,770 --> 01:03:22,210
But the stuff in green is optional.

1130
01:03:22,210 --> 01:03:25,680
The white are required,
like predefined names.

1131
01:03:25,680 --> 01:03:30,750
And the light blue are things
that vary depending on the table.

1132
01:03:30,750 --> 01:03:34,640
So that's what's going on with
the color scheme here, up there.

1133
01:03:34,640 --> 01:03:40,250
>> So if we want to update just those rows
of the people who live in New York,

1134
01:03:40,250 --> 01:03:43,490
so what we would do if we said UPDATE?

1135
01:03:43,490 --> 01:03:46,320
So table is where we put
the name of our table.

1136
01:03:46,320 --> 01:03:49,170
Let's just say the name
of our table is table one.

1137
01:03:49,170 --> 01:03:52,515
So we want to UPDATE table one.

1138
01:03:52,515 --> 01:03:57,470
And we want to set--
what do we want to set?

1139
01:03:57,470 --> 01:04:05,160
Well we want to say, so column-- PHP
treats rows as unique identifiers.

1140
01:04:05,160 --> 01:04:07,930
And then columns are
the different fields

1141
01:04:07,930 --> 01:04:09,940
of those elements of the database.

1142
01:04:09,940 --> 01:04:14,210
>> So the first element of the database
has a name of Sam, superpower of CS50,

1143
01:04:14,210 --> 01:04:16,210
and a hometown of Milwaukee.

1144
01:04:16,210 --> 01:04:20,710
So if we said set, let's look at
the parameters again that set takes.

1145
01:04:20,710 --> 01:04:23,880
We have column equals value.

1146
01:04:23,880 --> 01:04:27,290
So we want to say some
column-- which remember

1147
01:04:27,290 --> 01:04:31,850
is a field-- we want to see a
field equal to something new.

1148
01:04:31,850 --> 01:04:42,340
>> So if we just said update
table 1, set name equal Elliot.

1149
01:04:42,340 --> 01:04:46,310
Get some people from the
new section in on this.

1150
01:04:46,310 --> 01:04:51,540
But if we just did update table 1
set name equal Elliot, what would

1151
01:04:51,540 --> 01:04:55,530
the table look like after that?

1152
01:04:55,530 --> 01:04:56,410
People have any idea?

1153
01:04:56,410 --> 01:04:59,710

1154
01:04:59,710 --> 01:05:00,210
Yeah.

1155
01:05:00,210 --> 01:05:03,195
>> AUDIENCE: Everything in that
row would become Elliot.

1156
01:05:03,195 --> 01:05:04,570
SPEAKER: Everything in which row?

1157
01:05:04,570 --> 01:05:06,067
AUDIENCE: In the first row.

1158
01:05:06,067 --> 01:05:07,150
SPEAKER: In the first row?

1159
01:05:07,150 --> 01:05:09,724
Why the first row?

1160
01:05:09,724 --> 01:05:10,890
I don't mean to pick on you.

1161
01:05:10,890 --> 01:05:13,287
>> AUDIENCE: Maybe everything
in the whole table?

1162
01:05:13,287 --> 01:05:15,120
SPEAKER: Everything in
the whole table, yes.

1163
01:05:15,120 --> 01:05:19,520
And that's exactly right because-- I
was just helping you out a little bit

1164
01:05:19,520 --> 01:05:22,650
there-- because we omitted
the optional WHERE clause.

1165
01:05:22,650 --> 01:05:27,260
If you don't have the WHERE
clause, what this command will do

1166
01:05:27,260 --> 01:05:32,240
is it'll work with every
single row in the table.

1167
01:05:32,240 --> 01:05:35,430
Everyone's name will
become Elliott, basically,

1168
01:05:35,430 --> 01:05:37,360
which Elliot is very happy about.

1169
01:05:37,360 --> 01:05:40,070
Or Yanni, one of the two.

1170
01:05:40,070 --> 01:05:42,490
But everyone's name will change.

1171
01:05:42,490 --> 01:05:47,880
>> So the way we use the WHERE clause--
and this applies to all of the WHEREs

1172
01:05:47,880 --> 01:05:51,410
that are in each of
these different things.

1173
01:05:51,410 --> 01:05:54,380
So you'll notice that SET
has column equal value.

1174
01:05:54,380 --> 01:05:55,190
And so does WHERE.

1175
01:05:55,190 --> 01:06:00,040
But these are different
types of statements.

1176
01:06:00,040 --> 01:06:04,400
So the column equals value
in SET is in assignment.

1177
01:06:04,400 --> 01:06:08,320
Like we're saying we want
to set name equal to Elliot.

1178
01:06:08,320 --> 01:06:15,390
But in the WHERE clauses,
these are equality statements.

1179
01:06:15,390 --> 01:06:20,410
So let's say we only wanted to
change the person's name to Elliot

1180
01:06:20,410 --> 01:06:23,940
if their name was Ryan, let's say.

1181
01:06:23,940 --> 01:06:24,920
>> So when we say

1182
01:06:24,920 --> 01:06:32,700
>> WHERE name equals Ryan, that
would successfully only change

1183
01:06:32,700 --> 01:06:37,440
the name-- it would only
change the name field in rows

1184
01:06:37,440 --> 01:06:40,770
where the name field is equal to Ryan.

1185
01:06:40,770 --> 01:06:44,430
So if we had multiple people
named Ryan, all of their names

1186
01:06:44,430 --> 01:06:45,730
would change to Elliot.

1187
01:06:45,730 --> 01:06:48,169
>> This is similar to the example
of if a fault line splits

1188
01:06:48,169 --> 01:06:50,960
New York City and everyone has to
move to New Haven, the way we can

1189
01:06:50,960 --> 01:06:56,570
do that in one statement is UPDATE
table1 SET hometown = New Haven

1190
01:06:56,570 --> 01:07:00,210
where hometown equals New York City.

1191
01:07:00,210 --> 01:07:03,410
This is the power of
the UPDATE statement.

1192
01:07:03,410 --> 01:07:10,530
We can select any number of
rows through true statements

1193
01:07:10,530 --> 01:07:12,860
about the fields in those rows.

1194
01:07:12,860 --> 01:07:19,510
We can't say UPDATE table1 set
name = Elliot WHERE row = 1,

1195
01:07:19,510 --> 01:07:24,820
except that we can if we say ID = 1.

1196
01:07:24,820 --> 01:07:27,350

1197
01:07:27,350 --> 01:07:29,830
>> So we're going to be
working with equality

1198
01:07:29,830 --> 01:07:32,830
of fields, equality of columns.

1199
01:07:32,830 --> 01:07:38,030
But using the ID field is a way to
select individual rows specifically,

1200
01:07:38,030 --> 01:07:43,210
because the ID field is a unique
identifier in a SQL database.

1201
01:07:43,210 --> 01:07:45,860
So like updating row one, ID equals 1.

1202
01:07:45,860 --> 01:07:49,560
Updating row two, just
change that ID number.

1203
01:07:49,560 --> 01:07:51,610
But the power of the
WHERE statement is that we

1204
01:07:51,610 --> 01:07:57,480
can update things based on what their
current values of certain things are.

1205
01:07:57,480 --> 01:07:58,155
Yes Elliot?

1206
01:07:58,155 --> 01:08:02,678
>> AUDIENCE: And what if you want to--
again, this is another question.

1207
01:08:02,678 --> 01:08:07,660
But my first question was,
where is this happening?

1208
01:08:07,660 --> 01:08:09,130
Where am I updating this?

1209
01:08:09,130 --> 01:08:11,100
Is this in a PHP code?

1210
01:08:11,100 --> 01:08:13,379
>> SPEAKER: Where you update, yes.

1211
01:08:13,379 --> 01:08:15,170
We're going to talk
about where all of this

1212
01:08:15,170 --> 01:08:18,729
happens sort of once we go
through all the commands.

1213
01:08:18,729 --> 01:08:21,130
But what you need to
know for now is basically

1214
01:08:21,130 --> 01:08:26,279
that your SQL database
exists as something

1215
01:08:26,279 --> 01:08:30,090
to be accessed by the query
function, which CS50 defines.

1216
01:08:30,090 --> 01:08:33,800
So if you use the query function,
you can access this table.

1217
01:08:33,800 --> 01:08:39,529
>> So you will be sending these
commands to your table in PHP files

1218
01:08:39,529 --> 01:08:41,420
through the query function.

1219
01:08:41,420 --> 01:08:45,410
You can also play around
with your table directly.

1220
01:08:45,410 --> 01:08:49,050
And that's the best way to
test these sorts of commands.

1221
01:08:49,050 --> 01:08:52,720
And we'll go through exactly how
to do that in just a little bit.

1222
01:08:52,720 --> 01:08:54,910
>> So that's UPDATE command.

1223
01:08:54,910 --> 01:08:57,939
And the rest of the commands
are going to be sort of similar,

1224
01:08:57,939 --> 01:08:59,069
working on similar things.

1225
01:08:59,069 --> 01:09:02,740
The INSERT INTO is probably
the most different from UPDATE.

1226
01:09:02,740 --> 01:09:06,170
I'm going to leave that up there for
just a little bit and work over here.

1227
01:09:06,170 --> 01:09:10,215
So INSERT INTO, you'll see
that table is still the same.

1228
01:09:10,215 --> 01:09:17,010
You want to INSERT INTO.

1229
01:09:17,010 --> 01:09:20,286
The capitalization, SQL
is case insensitive.

1230
01:09:20,286 --> 01:09:22,160
So you don't have to
capitalize these things.

1231
01:09:22,160 --> 01:09:27,960
By convention, the words
in white are capitalized.

1232
01:09:27,960 --> 01:09:31,590
But I also color coded them.

1233
01:09:31,590 --> 01:09:34,390
The only reason that you capitalize
those when you're typing them

1234
01:09:34,390 --> 01:09:36,609
is just to emphasize
that those are constants.

1235
01:09:36,609 --> 01:09:39,189
And so you can either look at
the capitalization or the fact

1236
01:09:39,189 --> 01:09:40,740
that I've colored them differently.

1237
01:09:40,740 --> 01:09:44,910
>> So we've got INSERT INTO,
let's do table1 again.

1238
01:09:44,910 --> 01:09:45,930
This is all on one line.

1239
01:09:45,930 --> 01:09:48,609
I'm just separating it by
the different statements.

1240
01:09:48,609 --> 01:09:52,399
So don't worry about the fact that
table1 made it onto the second line.

1241
01:09:52,399 --> 01:09:56,130
>> So we want to INSERT
INTO table1 some values.

1242
01:09:56,130 --> 01:09:58,922
And you'll notice the optional
bit, which I'll get to in a second.

1243
01:09:58,922 --> 01:09:59,755
So we've got VALUES.

1244
01:09:59,755 --> 01:10:03,640

1245
01:10:03,640 --> 01:10:08,100
>> So let's say we want to add Andi
to our table, because we miss Andi.

1246
01:10:08,100 --> 01:10:09,390
Andi is sick.

1247
01:10:09,390 --> 01:10:12,490
So let's add Andi to our table.

1248
01:10:12,490 --> 01:10:15,150
Remember that the ID number
is updated automatically.

1249
01:10:15,150 --> 01:10:17,320
So the only fields we
need to worry about

1250
01:10:17,320 --> 01:10:20,230
are name, superpower, and hometown.

1251
01:10:20,230 --> 01:10:23,660
>> And so the way that we do that,
looking at our syntax, is we've

1252
01:10:23,660 --> 01:10:28,780
just got a parentheses, with comma
separated values, each of which

1253
01:10:28,780 --> 01:10:29,890
is a value.

1254
01:10:29,890 --> 01:10:35,530
So if we wanted to insert Andi into our
table, all we have to do is right Andi.

1255
01:10:35,530 --> 01:10:38,630
What's Andi's superpower,
people in Andi's section?

1256
01:10:38,630 --> 01:10:45,406

1257
01:10:45,406 --> 01:10:47,545
She like flight, or like
speed, or something.

1258
01:10:47,545 --> 01:10:48,920
What do we already have up there?

1259
01:10:48,920 --> 01:10:53,425
We have CS50, flight,
speed, and strength.

1260
01:10:53,425 --> 01:10:54,850
>> AUDIENCE: Time travel.

1261
01:10:54,850 --> 01:10:56,180
>> SPEAKER: Time travel, amazing.

1262
01:10:56,180 --> 01:11:04,280
So we've got Andi, time
travel, and her hometown.

1263
01:11:04,280 --> 01:11:05,530
That's a really good question.

1264
01:11:05,530 --> 01:11:09,210
New York City, unless someone knows.

1265
01:11:09,210 --> 01:11:13,600
Everyone's from New York is the
lesson to take away from today.

1266
01:11:13,600 --> 01:11:17,710
>> So this statement would
insert, as a fifth row,

1267
01:11:17,710 --> 01:11:21,900
with the superpower time travel
and a hometown of New York City.

1268
01:11:21,900 --> 01:11:25,660
But the optional field
is basically a way

1269
01:11:25,660 --> 01:11:30,090
to specify exactly which columns
you want to insert things in.

1270
01:11:30,090 --> 01:11:33,710
>> The way that we're doing it now,
Andi, time travel, New York City,

1271
01:11:33,710 --> 01:11:38,150
is going in the exact order of our
table-- name, superpower, hometown.

1272
01:11:38,150 --> 01:11:42,290
And if you wanted to do
something other than that,

1273
01:11:42,290 --> 01:11:44,970
like say you didn't know
someone's superpower,

1274
01:11:44,970 --> 01:11:47,660
like how I didn't know Andi's
superpower at the beginning.

1275
01:11:47,660 --> 01:11:50,450
So all I knew was her
name and her hometown.

1276
01:11:50,450 --> 01:11:54,550
What I could do is I could
do-- I'll erase this quick.

1277
01:11:54,550 --> 01:11:57,910

1278
01:11:57,910 --> 01:12:00,090
>> I want to only update the columns.

1279
01:12:00,090 --> 01:12:04,100
And this is where the optional
column list comes into play.

1280
01:12:04,100 --> 01:12:09,185
I only want to update name and hometown.

1281
01:12:09,185 --> 01:12:12,650

1282
01:12:12,650 --> 01:12:16,480
And then I will say VALUES.

1283
01:12:16,480 --> 01:12:24,430
I'll do Andi and New York City.

1284
01:12:24,430 --> 01:12:28,980
>> If I had omitted the list of columns
and just done these two things,

1285
01:12:28,980 --> 01:12:32,450
where would New York City have gone?

1286
01:12:32,450 --> 01:12:35,900
Which column would New York
City have been placed in?

1287
01:12:35,900 --> 01:12:38,950
People have any idea?

1288
01:12:38,950 --> 01:12:40,160
Superpower, exactly.

1289
01:12:40,160 --> 01:12:41,890
>> So this will just go in order.

1290
01:12:41,890 --> 01:12:45,530
And once it reaches the end of the
list, it'll just stop filling things in.

1291
01:12:45,530 --> 01:12:49,080
And the values that it'll stick in
all the columns will just be NULL.

1292
01:12:49,080 --> 01:12:51,840
So because we specified
name and hometown,

1293
01:12:51,840 --> 01:12:56,110
we're going to have ID 5,
name Andi, superpower NULL.

1294
01:12:56,110 --> 01:12:58,750
So superpower is an uninitialized value.

1295
01:12:58,750 --> 01:13:01,340
You won't necessarily get the
same Valgrind errors if you try

1296
01:13:01,340 --> 01:13:01,970
and access it.

1297
01:13:01,970 --> 01:13:05,160
Everything will be nicely zeroed
out, because NULL is a value in SQL.

1298
01:13:05,160 --> 01:13:06,780
That is a constant.

1299
01:13:06,780 --> 01:13:08,980
And then hometown will be New York City.

1300
01:13:08,980 --> 01:13:11,860
So that's the INSERT INTO command.

1301
01:13:11,860 --> 01:13:13,610
Before we move, there's
two more commands.

1302
01:13:13,610 --> 01:13:19,060
Do people have any questions about
UPDATE, about INSERT INTO, about SQL

1303
01:13:19,060 --> 01:13:21,556
generally before we move
onto our final bits?

1304
01:13:21,556 --> 01:13:25,500

1305
01:13:25,500 --> 01:13:26,910
People feel good, great.

1306
01:13:26,910 --> 01:13:27,410
Love it.

1307
01:13:27,410 --> 01:13:29,480
So let's talk about SELECT.

1308
01:13:29,480 --> 01:13:33,445
Going ditch UPDATE over here.

1309
01:13:33,445 --> 01:13:35,720
>> And SELECT is going to be very similar.

1310
01:13:35,720 --> 01:13:38,790
The goal of SELECT,
SELECT's purpose in life

1311
01:13:38,790 --> 01:13:45,910
is to give you a bunch of columns
that satisfy certain conditions.

1312
01:13:45,910 --> 01:13:48,230
And when I say satisfy
certain conditions,

1313
01:13:48,230 --> 01:13:50,800
your mind might immediately
go back to that WHERE clause

1314
01:13:50,800 --> 01:13:52,090
that came up in UPDATE.

1315
01:13:52,090 --> 01:13:54,880
And that clause is
exactly there in SELECT.

1316
01:13:54,880 --> 01:14:06,020
>> If we don't put the WHERE
clause and we say SELECT name,

1317
01:14:06,020 --> 01:14:16,490
hometown-- spelled that a little
wrong-- name, hometown FROM table1.

1318
01:14:16,490 --> 01:14:19,690
If we just say that, what SELECT
is going to give us is it's

1319
01:14:19,690 --> 01:14:23,730
going to give us a
double-- a table, rather.

1320
01:14:23,730 --> 01:14:27,450
A double array if we're
thinking about in PHP senses.

1321
01:14:27,450 --> 01:14:33,239
But it's just going to give us a
double array of two columns-- name,

1322
01:14:33,239 --> 01:14:33,780
and hometown.

1323
01:14:33,780 --> 01:14:36,400

1324
01:14:36,400 --> 01:14:38,130
And it will ignore ID.

1325
01:14:38,130 --> 01:14:41,310
And it will ignore superpower.

1326
01:14:41,310 --> 01:14:44,696
And it'll just give us every
single row of that table.

1327
01:14:44,696 --> 01:14:46,570
So if we just inserted
Andi, we'll have Andi.

1328
01:14:46,570 --> 01:14:48,605
And we'll have the original four.

1329
01:14:48,605 --> 01:14:53,720
If they've been updated, that will
be reflected, et cetera, et cetera.

1330
01:14:53,720 --> 01:14:56,520
>> So this is because we
didn't use the WHERE clause.

1331
01:14:56,520 --> 01:14:59,200
But we can use it in exactly the
same way we used it in UPDATE.

1332
01:14:59,200 --> 01:15:05,310
If we only want a table of the names
and super powers of people living

1333
01:15:05,310 --> 01:15:13,430
in New York, we can execute a statement
like SELECT name, superpower--

1334
01:15:13,430 --> 01:15:27,190
I'm just going to leave that-- FROM
table1 WHERE hometown = New York City.

1335
01:15:27,190 --> 01:15:33,370
>> So this goes to show that you can
get totally different columns,

1336
01:15:33,370 --> 01:15:36,920
and then put columns that you're not
even getting back in the WHERE clause.

1337
01:15:36,920 --> 01:15:39,200
We don't even want the
hometown of everyone.

1338
01:15:39,200 --> 01:15:41,920
But we want the name and
the superpower of people

1339
01:15:41,920 --> 01:15:43,817
whose hometown is New York City.

1340
01:15:43,817 --> 01:15:45,650
So that's something we
can do with the WHERE

1341
01:15:45,650 --> 01:15:49,112
clause is we can deal with columns
that we don't necessarily want back.

1342
01:15:49,112 --> 01:15:52,320
In the same way in UPDATE, we can deal
with columns that we don't necessarily

1343
01:15:52,320 --> 01:15:53,270
want to update.

1344
01:15:53,270 --> 01:15:58,890
We can update the city of everyone
who's name is Sam, for instance.

1345
01:15:58,890 --> 01:16:02,080
We can update the city of
everyone whose ID number is 2.

1346
01:16:02,080 --> 01:16:04,960
So just update the
city of the second row

1347
01:16:04,960 --> 01:16:08,220
where we don't have to deal with
necessary the common question.

1348
01:16:08,220 --> 01:16:13,264
>> And DELETE is, as you'd
expect, DELETE FROM table1.

1349
01:16:13,264 --> 01:16:14,930
And then we've got another WHERE clause.

1350
01:16:14,930 --> 01:16:17,940
So we can say WHERE ID = 1.

1351
01:16:17,940 --> 01:16:18,950
Delete the first row.

1352
01:16:18,950 --> 01:16:23,240
And DELETE will always delete a row,
or it will delete some number of rows.

1353
01:16:23,240 --> 01:16:26,990
DELETE FROM table WHERE
hometown = New York City

1354
01:16:26,990 --> 01:16:28,740
will delete everyone in New York City.

1355
01:16:28,740 --> 01:16:30,985
That's if there was a
sudden tragic plague

1356
01:16:30,985 --> 01:16:33,360
and you just wanted to remove
everyone from the table who

1357
01:16:33,360 --> 01:16:35,760
lived in a certain city
that was hit by the plague.

1358
01:16:35,760 --> 01:16:38,050
May they rest in peace.

1359
01:16:38,050 --> 01:16:43,849
>> These are the four SQL commands
that you will need to use.

1360
01:16:43,849 --> 01:16:45,390
You might not even need use them all.

1361
01:16:45,390 --> 01:16:47,690
But these are the four
that CS50 expects you

1362
01:16:47,690 --> 01:16:53,630
to be comfortable with going into
both quiz 1 and also pset7 and pset8.

1363
01:16:53,630 --> 01:16:55,820
>> There's just that table again.

1364
01:16:55,820 --> 01:16:58,930
In this one, Roy's superpower has
been updated to laser beams, which

1365
01:16:58,930 --> 01:17:00,880
is an example I did not use.

1366
01:17:00,880 --> 01:17:05,480
I don't know which one
Roy prefers, but strength.

1367
01:17:05,480 --> 01:17:07,670
Roy has a superpower of strength.

1368
01:17:07,670 --> 01:17:09,090
Katherine did not make it today.

1369
01:17:09,090 --> 01:17:10,260
That's unfortunate.

1370
01:17:10,260 --> 01:17:11,260
But she has super speed.

1371
01:17:11,260 --> 01:17:13,780

1372
01:17:13,780 --> 01:17:14,670
>> Well that was PHP.

1373
01:17:14,670 --> 01:17:19,410
Before we talk about MVC, does
anyone have questions about PHP?

1374
01:17:19,410 --> 01:17:23,864
Now SQL, or PHP if you suddenly have
come up with a question about PHP?

1375
01:17:23,864 --> 01:17:27,560

1376
01:17:27,560 --> 01:17:28,460
Great.

1377
01:17:28,460 --> 01:17:29,920
All right, we're all set then.

1378
01:17:29,920 --> 01:17:33,660
>> So talking a little bit
about model view controllers,

1379
01:17:33,660 --> 01:17:38,770
let's go back to some
of the stuff in pset7.

1380
01:17:38,770 --> 01:17:42,470
So what model view
controller is-- I'm not

1381
01:17:42,470 --> 01:17:45,660
going to save my changes to login
because I totally butchered it.

1382
01:17:45,660 --> 01:17:49,220
But basically we have two
separate things going on.

1383
01:17:49,220 --> 01:17:52,390
We have a public
directory which contains

1384
01:17:52,390 --> 01:17:56,460
the code that's going to be executed
and the web pages that will be visited.

1385
01:17:56,460 --> 01:17:58,780
And we also have this views directory.

1386
01:17:58,780 --> 01:18:01,780
And views contains templates.

1387
01:18:01,780 --> 01:18:04,390
>> This is what the function
render-- we saw the render

1388
01:18:04,390 --> 01:18:08,240
function in a bunch of the PHP code
that CS50 has already written for you,

1389
01:18:08,240 --> 01:18:10,550
that takes in certain parameters.

1390
01:18:10,550 --> 01:18:14,510
What that code is doing
is it's going into views,

1391
01:18:14,510 --> 01:18:18,000
which are sets of like
prewritten HTML code,

1392
01:18:18,000 --> 01:18:20,720
and it's inserting values
into certain places.

1393
01:18:20,720 --> 01:18:23,990
This is how when you
go into CS50 Finance,

1394
01:18:23,990 --> 01:18:25,760
the same header is on every page.

1395
01:18:25,760 --> 01:18:28,130
The same footer is on every page.

1396
01:18:28,130 --> 01:18:31,880
This is because the way
that render works is it'll

1397
01:18:31,880 --> 01:18:36,720
automatically patch in that header and
viewer which you can find in views.

1398
01:18:36,720 --> 01:18:41,400
>> We actually can go into header, and
look, it's an HTML file with a head.

1399
01:18:41,400 --> 01:18:43,280
It's got some stylesheets.

1400
01:18:43,280 --> 01:18:48,450
You don't need to look at CSS
for pset7 if you don't want to.

1401
01:18:48,450 --> 01:18:50,560
But you can modify
them if you want, make

1402
01:18:50,560 --> 01:18:53,470
your Finance look a little different.

1403
01:18:53,470 --> 01:18:57,560
>> It's got some PHP in
the header a bit to see

1404
01:18:57,560 --> 01:19:01,240
if there's a different title
it should put in this header.

1405
01:19:01,240 --> 01:19:04,300
But just some other scripts,
and links, and other things.

1406
01:19:04,300 --> 01:19:08,700
Head ends, body starts, and oops,
we have this weird little end bit.

1407
01:19:08,700 --> 01:19:14,730
And there's a div, just like
a formless kind of element

1408
01:19:14,730 --> 01:19:17,120
that has an idea of middle.

1409
01:19:17,120 --> 01:19:22,450
>> And then when we see footer,
we have the end of a div.

1410
01:19:22,450 --> 01:19:25,000
We have a bottom, which is
where the footer text is.

1411
01:19:25,000 --> 01:19:26,770
End of div, end of body, end of HTML.

1412
01:19:26,770 --> 01:19:29,070
>> So what render is
doing is render is sort

1413
01:19:29,070 --> 01:19:33,150
of patching up header, a
different PHP file that

1414
01:19:33,150 --> 01:19:37,110
will contain the actual things that
you'll view, like your table of stocks

1415
01:19:37,110 --> 01:19:39,690
if you are buying or selling stocks.

1416
01:19:39,690 --> 01:19:41,480
And then it'll add in the footer.

1417
01:19:41,480 --> 01:19:44,890
And the model view
controller idea is that we

1418
01:19:44,890 --> 01:19:49,590
want to separate how
things look from the code.

1419
01:19:49,590 --> 01:19:53,420
It's we want to separate the frontend
and the backend, where the frontend is

1420
01:19:53,420 --> 01:20:00,440
the stuff that the user sees, the nice
visuals-- HTML, CSS, things like that,

1421
01:20:00,440 --> 01:20:02,320
images, et cetera.

1422
01:20:02,320 --> 01:20:05,780
And the backend is PHP.

1423
01:20:05,780 --> 01:20:07,710
This is code that you write.

1424
01:20:07,710 --> 01:20:10,240
This is where the code that's
doing actual operations.

1425
01:20:10,240 --> 01:20:12,400
This is when you're adding
a stock to your table,

1426
01:20:12,400 --> 01:20:14,890
when you're buying and
selling, that's backend.

1427
01:20:14,890 --> 01:20:20,210
>> And we can, as you saw,
including PHP directly in HTML.

1428
01:20:20,210 --> 01:20:23,210
So what we could have done for
this assignment is just had

1429
01:20:23,210 --> 01:20:26,200
an HTML file for each page, like login.

1430
01:20:26,200 --> 01:20:30,260
And then on that page, just
had a huge block of PHP code,

1431
01:20:30,260 --> 01:20:33,822
including all of the code that
that page specifically would need.

1432
01:20:33,822 --> 01:20:35,780
And then we could have
done that for portfolio.

1433
01:20:35,780 --> 01:20:40,250
We could have done all of the buying
and selling within the individual pages.

1434
01:20:40,250 --> 01:20:43,680
>> But because we're rendering
separately from where

1435
01:20:43,680 --> 01:20:46,660
we're writing the backend
code, we can easily

1436
01:20:46,660 --> 01:20:52,660
change how things look without
changing every single file.

1437
01:20:52,660 --> 01:20:55,460
We do things like just add
a new div to the bottom

1438
01:20:55,460 --> 01:21:00,720
of-- Hello I modified the footer.

1439
01:21:00,720 --> 01:21:03,710
You can just do stuff like that.

1440
01:21:03,710 --> 01:21:07,250
But also, you can change
the entire visual layout

1441
01:21:07,250 --> 01:21:09,290
without affecting what's
going in the backend.

1442
01:21:09,290 --> 01:21:12,000
And you can change the
entire backend and still

1443
01:21:12,000 --> 01:21:13,900
have it look just like it did before.

1444
01:21:13,900 --> 01:21:14,400
This

1445
01:21:14,400 --> 01:21:16,170
>> Is the idea of model view controller.

1446
01:21:16,170 --> 01:21:19,992
And it's actually an imposed paradigm
in some of the programming languages

1447
01:21:19,992 --> 01:21:21,700
you might want to use
for final projects.

1448
01:21:21,700 --> 01:21:25,100
If you do iOS development,
they have views,

1449
01:21:25,100 --> 01:21:29,120
which is what you see on the iPhone, and
then backend as like a separate thing.

1450
01:21:29,120 --> 01:21:31,260
>> You can think about a little bit.

1451
01:21:31,260 --> 01:21:35,190
There's a lot of binaries in
computer science, which is funny,

1452
01:21:35,190 --> 01:21:37,270
because everything's in binary.

1453
01:21:37,270 --> 01:21:38,550
I didn't plan that.

1454
01:21:38,550 --> 01:21:41,590
That was a pun unintended.

1455
01:21:41,590 --> 01:21:43,860
Yes, pun not intended.

1456
01:21:43,860 --> 01:21:49,070
>> But like .h files and .c files, there's
a lot of separating of things that we

1457
01:21:49,070 --> 01:21:49,900
might not need.

1458
01:21:49,900 --> 01:21:54,330
So we can just edit the h files, or
someone can just see a .h file and know

1459
01:21:54,330 --> 01:21:57,650
exactly the functions that are in the
.c file without necessarily knowing

1460
01:21:57,650 --> 01:21:58,870
their implementation.

1461
01:21:58,870 --> 01:22:02,800
This idea of separating components
that depend on each other

1462
01:22:02,800 --> 01:22:06,990
but can sort of access each other
through different channels, passing

1463
01:22:06,990 --> 01:22:09,310
of variables, just
include statements, things

1464
01:22:09,310 --> 01:22:14,440
like that, this principle
helps to create applications

1465
01:22:14,440 --> 01:22:17,080
that can be more easily
edited by multiple people,

1466
01:22:17,080 --> 01:22:20,440
can be more easily changed
or modified on a big scale,

1467
01:22:20,440 --> 01:22:24,880
and are easier to
debug in a lot of ways.

1468
01:22:24,880 --> 01:22:28,254
>> Really quick, I have
a few tips for pset7,

1469
01:22:28,254 --> 01:22:31,420
which I'll make full screen so you not
just looking at the-- tip tip tippee.

1470
01:22:31,420 --> 01:22:33,964

1471
01:22:33,964 --> 01:22:35,130
There aren't that many tips.

1472
01:22:35,130 --> 01:22:38,060
>> But I mentioned PHP is hard to debug.

1473
01:22:38,060 --> 01:22:39,290
Double and triple check it.

1474
01:22:39,290 --> 01:22:41,550
If your code is just not
showing up on the page,

1475
01:22:41,550 --> 01:22:46,240
it's probably a PHP error, sorry.

1476
01:22:46,240 --> 01:22:48,570
>> You never need to look at
CSS if you don't want to.

1477
01:22:48,570 --> 01:22:52,150
But once you're finished, it can be
a nice little fun thing to just go in

1478
01:22:52,150 --> 01:22:54,770
and mess with the CSS parameters.

1479
01:22:54,770 --> 01:22:58,700
CSS and HTML are an example of a model
view controller style thing too, right?

1480
01:22:58,700 --> 01:23:02,150
You could have style tags
inside of HTML elements.

1481
01:23:02,150 --> 01:23:04,800
But if you sort of
outsourcing them to CSS,

1482
01:23:04,800 --> 01:23:08,180
they're easier to edit, and play
around with, and have fun with.

1483
01:23:08,180 --> 01:23:10,816
>> Treat CS50 helper
functions as black boxes.

1484
01:23:10,816 --> 01:23:12,940
You don't need to know
exactly what render's doing,

1485
01:23:12,940 --> 01:23:16,770
but trust it to always do the right
thing depending on what you pass it,

1486
01:23:16,770 --> 01:23:17,690
things like this.

1487
01:23:17,690 --> 01:23:21,040
And I would recommend
watching David's walkthrough,

1488
01:23:21,040 --> 01:23:24,490
going through all the
stuff, not just the todos,

1489
01:23:24,490 --> 01:23:26,960
but you really can treat
these as black boxes.

1490
01:23:26,960 --> 01:23:29,280
Don't go into these
functions looking for bugs.

1491
01:23:29,280 --> 01:23:33,510
>> And welcome the return
of our overlord Zamyla.

1492
01:23:33,510 --> 01:23:34,010
Great.

1493
01:23:34,010 --> 01:23:40,430
>> Are there any final questions before
we sort of bounce for the day?

1494
01:23:40,430 --> 01:23:42,610
Am I still live?

1495
01:23:42,610 --> 01:23:44,700
Great.

1496
01:23:44,700 --> 01:23:47,120
Hi livestream people.

1497
01:23:47,120 --> 01:23:47,620
Great.

1498
01:23:47,620 --> 01:23:50,260
Are there anymore questions?

1499
01:23:50,260 --> 01:23:50,760
No?

1500
01:23:50,760 --> 01:23:52,884
>> And then I think we're
good to go for today.

1501
01:23:52,884 --> 01:23:55,550
I'll stick around a little bit
afterward if people had questions

1502
01:23:55,550 --> 01:23:57,480
they were afraid to ask on the stream.

1503
01:23:57,480 --> 01:23:59,790
But otherwise, have a good day.

1504
01:23:59,790 --> 01:24:01,933