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Autoloading is the art of only loading what you actually need. It is done very efficiently in PHP, and when a class is requested you can register an autoloader to then locate and include the class for you. When combined with an autoloading standard such as PSR-0 or PSR-4 this is very simple.
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Autoloading is one of [UNKNOWN] most
useful features when it comes to
0:00
object-oriented code.
0:03
Gone are the days of being forced to
include a huge list of code on
0:04
the off chance that later, some of your
code might need it.
0:07
All you need to do is register an
autoloader,
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then make sure your autoloader and file
wants to use the same rules.
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Let's take a look at how we might make our
own autoloader.
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Let's take the code from our last lesson
and adopt it to use auto loading.
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Auto loading is important because as our
application grows it
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seems only logical that the code we depend
on grows too.
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As we develop, we'll most likely have more
than just HTTP and
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Twitter but all sorts of other includes
too.
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To save us including each of them
manually, let's make our own auto
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loader allowing other developers or future
you to add dependencies easily.
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Let's tuck this autoloader away in a
bootstrap file to keep our index
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nice and clean.
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We go to our workspace, and add new file.
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We can just create bootstrap.php and we'll
just shove it in the root here.
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Then the code that we enter will look like
this.
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Here we can see an autoloader being
registered with an anonymous function.
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The anonymous function acts as a call
back.
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Basically whenever a class is referenced
the PHP does not recognize it will
1:05
hit this callback and pass the name of
the class in as a string argument,
1:09
which we can see here on line three.
1:13
Our callback then accepts that string as
an argument.
1:15
Line four will replace any back slashes
with a forward slash.
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PHP knows this means a directory separator
regardless of your operating system.
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The reason we have two backslashes in the
first argument is that only putting one
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backslash in here would escape the single
quote, and that'll cause a syntax error.
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So we take one of these slashes out here,
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you see the syntax is all changed, and
that is broken.
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So you need two backslashes here.
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We then create a new string starting with
the current directory.
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Appending the source src folder, and use
that new class name and
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suffix dot PHP on the end of the string to
make a full file path.
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Now we include this file, otherwise PHP
won't know how to use it.
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Let's go back to index.php and put this
all together.
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So, we no longer need to include these
files manually, so
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we can delete this line.
2:02
And we can change this include here so
instead of including one
2:02
of the classes directly we can say that
we'd like to include bootstrap.
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Let's try having a look at this in preview
mode and see if it worked.
2:11
Perfect.
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Even though we did not explicitly include
the classes we wanted as we did in
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the last lesson, PHP is still happy
because it knows where to find the code.
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Now, it's important to have a base
understanding of making your
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own autoloaders.
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But it might not always be a great idea to
roll your own.
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For years, autoloading code in PHP was a
bit hit or miss.
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And this was down to everyone wanting to
write their own auto-loaders and
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organizing their code in their own
different ways.
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This meant implementing 10 different
packages could mean 10 different styles of
2:40
auto-loading being used.
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These days, we have the PSL zero standard
and a new and shiny standard called PSL 4.
2:46
These two standards were written by the
PHP Framework Interoperability Group,
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to make autoloading dependencies
incredibly easy.
2:55
We'll look more at how PSR4 works with
Composer in the upcoming lessons.
2:59
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