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I've an idea!

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Let's master PHP namespaces...

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and let's do it in under 5 minutes.

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Sip some coffee...

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let's go! Meet Foo: a perfectly
boring PHP class.

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Say hi Foo!

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Hilarious.

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To instantiate our favorite new class,
I'll move over to a different file

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and say - drumroll - $foo = new Foo().

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Tada! We can even call a method
on it: $foo->doAwesomeThings().

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Will it work?

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Of course!

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I can open a terminal and run:

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php some-other-file.php Right
now, Foo doesn't have a namespace!

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To make Foo more hipster, let's fix that.

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Above the class, add, how
about, namespace Acme\Tools.

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Usually the namespace of a class matches its
directory, but that's not technically required.

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I just invented this one!

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Congratulations!

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Our friend Foo now lives in a namespace.

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Putting a class in a namespace is a
lot like putting a file in a directory.

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To reference it, use the full, long
path to the class: Acme\Tools\Foo -

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just like you can use the absolute path
to reference a file in your filesystem.

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When we try the script now: It still works!

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And... that's really!

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Namespaces are basically a way to...

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make your class names longer!

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Add the namespace...

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then refer to the class using the
namespace plus the class name.

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That's it.

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But... having these long class names right
in the middle of your code is a bummer!

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To fix that, PHP namespaces have one
more special thing: the use statement.

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At the top of the file, add use
Acme\Tools\Foo as SomeFooClass.

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This creates a...

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sort of...

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"shortcut".

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Anywhere else in this file, we can now
just type SomeClassFoo and PHP will know

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that we're really referring to the
long class name: Acme\Tools\Foo.

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Or... if you leave off the as part, PHP
will assume you want this alias to be Foo.

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That's usually how code looks.

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So, namespaces make class names longer...

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and use statements allow us to create shortcuts
so we can use the "short" name in our code.

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In modern PHP code, pretty much all classes
you deal with will live in a namespace...

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except for core PHP classes.

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Yep, core PHP classes do
not live in a namespace...

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which kinda means that they
live at the "root" namespace -

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like a file at the root of your filesystem.

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Let's play with the core DateTime
object: $dt = new DateTime()

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and then echo $dt->getTimestamp()
with a line break.

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When we run the script: It works perfectly!

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But... now move that same code into the
doAwsomeThings method inside our friend Foo.

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Now try the code: Ah!

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It explodes!

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And check out that error!

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Class Acme\Tools\DateTime not found The
real class name should just be DateTime.

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So, why does PHP think it's Acme\Tools\DateTime?

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Because namespaces work like directories!

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Foo lives in Acme\Tools.

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When we just say DateTime,
it's the same as looking

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for a DateTime file inside
of an Acme/Tools directory.

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There are two ways to fix this.

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The first is to use the "fully
qualified" class name.

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So, \DateTime.

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Yep... that works just like a filesystem.

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Or... you can use DateTime...

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then remove the \ below.

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That's really the same thing:
there's no \ at the beginning

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of a use statement, but you
should pretend there is.

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This aliases DateTime to \DateTime.

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And... we're done!

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Namespaces make your class names longer, use
statements allow you to create "shortcuts"

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so you can use short names in your code

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and the whole system works exactly
like files inside directories.

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Have fun!