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>> DAVID MALAN: Let's improve the course's
homepage a bit further by

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generalizing those functions,
renderHeader and renderFooter, into,

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quite simply, render because after all,
they were nearly identical except

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for their names.

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How to do this?

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Well atop this file just, below where
we require helpers.php, let's call a

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new function, render, whose first
argument, let's say, shall be the name

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of a template, a file that's meant
to be plugged in there.

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Meanwhile, the second argument shall
remain an associative array, in this

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case an array containing a key for
title whose value is here CS50.

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Let's now look at helpers.php.

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>> In helpers.php, we now, of
course, have just one

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function defined, render.

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render takes now two arguments, which
we'll call template and data, the

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latter of whose default value
is still an empty array.

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But in this version of render, notice
that I now declare a local variable

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called path and assign it the value of
template, which, for instance, might

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be quote, unquote, "header" and
append to that string .php.

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In other words, let's assume for now
that if our template is called header,

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then that template will be implemented
in a file called, quite simply,

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header.php.

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>> Meanwhile, let's do a
quick sanity check.

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If that path exists, which we can
check by way of a file called

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file_exists, then let's extract the
associative array called data so that

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we have one or more local variables
in scope, and then let's

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require that path.

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Meanwhile, helpers.php looks quite
simply like this, exactly as before.

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>> But if we now look back at index.php,
notice that at the bottom of that

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file, we can similarly call
render, passing in as its

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sole argument footer.

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In this case, we don't need to pass in
an associative array because the

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footer template, recall, is just this.

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But now we have arguably an even
cleaner design because we've

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eliminated some of our otherwise
redundant code and consolidated into

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just one function, render.

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