PHP Namespaces in 120 SecondsΒΆ

Time to master PHP 5.3 namespaces! The good news is, namespaces are easy!

To prove it, we’ve challenged ourselves to explain them in 120 seconds.

Let’s go!

Meet Foo. He’s a PHP 5.2 class that does a lot of important things:

// Foo.php
class Foo
{
    public function doAwesomeFooThings()
    {

    }
}

Foo, say hi to the listener:

class Foo
{
    public function doAwesomeFooThings()
    {
        echo 'say Hi to the listeners';
    }
}

Ok, so Foo’s humor is a bit old too.

Using Foo is easy - simply “new Foo”:

// use_foo.php

require 'Foo.php';

$foo = new Foo();

To keep up with the times, let’s put Foo in a brand new PHP 5.3 namespace. A namespace is like a directory and by adding “namespace”, Foo now lives in AcmeTools:

// Foo.php

namespace Acme\Tools;

class Foo
{
    public function doAwesomeFooThings()
    {

    }
}

To use Foo, we have to call him by his fancy new name:

$foo = new \Acme\Tools\Foo();

This is just like referring to a file by its absolute path.

And that’s really it! Adding a namespace to a class is like organizing files from one directory, into a bunch of sub- directories. To refer to a class, use its fully-qualified name, starting with the slash. From here, it’s all gravy.

Since running around with this giant name is a drag, let’s add a shortcut:

use Acme\Tools\Foo as SomeFooClass;

$foo = new SomeFooClass();

The use statement lets us call \Acme\Tools\Foo class by a nickname. Heck, we can call it anything, or just let it default to Foo:

use \Acme\Tools\Foo;

$foo = new Foo();

Great? But what about old-school, non-namespaced PHP classes? For that, let’s pick on “DateTime”, a handy class that’s core to PHP, and got some new bells and whistles in PHP 5.3. For ever and ever, creating a new DateTime object looked the same: “new DateTime”:

// use_foo.php
// ...

$dt = new DateTime();

And if we’re in a normal file, this still works. But in a namespaced file, PHP thinks you’re talking about a class in the Acme\Tools namespace:

// Foo.php
namespace Acme\Tools;

class Foo
{
    public function doAwesomeFooThings()
    {
        echo 'Hi listeners';

        // Wrong! PHP will incorrectly think we mean Acme\Tools\DateTime!
        $dt = new DateTime();
    }
}

You can either refer to the class by its fully-qualified name - \DateTime:

$dt = new \DateTime();

or add a use statement:

// Foo.php
namespace Acme\Tools;

use \DateTime;

class Foo
{
    public function doAwesomeFooThings()
    {
        echo 'Hi listeners';

        // Yay!
        $dt = new DateTime();
    }
}

Yes, the use statement looks silly, but it tells PHP that when you say DateTime, you mean the non-namespaced class DateTime. Oh, and get rid of the beginning slash with the use statement - everything works completely the same with or without these, but you typically don’t see them:

use DateTime;

Ok bye!

Leave a comment!

  • 2015-07-21 weaverryan

    Ha, 120 seconds is definitely a rush! You can't slow down the video yet, but we're adding speed control really soon :)

  • 2015-07-21 Zoe Abe

    Quite helpful, many thanks! I realized it before I know I realized it (does that make sense? :P)
    But do you happen to have a 0.75x speed playback option? 120 seconds sound like a rush to me~~ :-D

  • 2015-03-27 sancoLgates

    great explanation, thanks :)
    i get it now!

  • 2015-03-20 Braxton Overby

    I got myself ready to sit down and read/watch for several minutes on how to properly use namespaces in PHP. I appreciate how easy this tutorial was to follow.

  • 2015-01-24 Sajeepan Yogenthiran

    useful tip :-) Thank you.

  • 2014-12-10 Alberto Maturano

    Yes, It would help :D

  • 2014-12-03 Jimmy James Atauje Hidalgo

    Very nice tutorial

  • 2014-11-13 weaverryan

    Hey r0ber!

    I wonder if (English) sub-titles would help? I want to do the most useful thing for our non-native English-speaking friends :).

    Thanks!

  • 2014-11-12 r0ber

    I am used to listen videos in english, but is very complicate to understand this videos, because she speak very fast.

  • 2014-10-27 weaverryan

    So nice, thanks Troy :)

  • 2014-10-25 Troy Close

    Brilliant. I just wasted my time reading two different tutorials on namespaces and still didn't understand it. Watched your video and got it immediately. Thanks Leanna and Ryan for uncomplicating this subject.

  • 2014-07-29 Century Media

    Great overview. Only thing I think it could use is to mention that the main use of namespaces is to stop method names conflicting. Aside from that great job!

  • 2014-06-04 weaverryan

    Hi there!

    Actually, namespaces and autoloading are 2 separate things, though in practice, due to PSR-0 autoloaders, they are quite related.

    Namespaces are all about basically making class names really long, and then giving us a "use" statement to help shorten things. On its own, it doesn't help with removing the require/include statements. So you're right, on their own, namespaces actually *add* code and make things longer. Really, namespaces weren't created for you and I, they were created for library authors to avoid name collisions (like you mentioned). For us, they just make things longer :).

    But in practice (and you're totally right about this part), if you use namespaces properly, AND you use a PSR-0/PSR-4 autoloader (like the one provided in Composer), then you'll be able to remove your require/include statements. The autoloader basically leverages namespaces to do this, but namespaces on their own don't allow you to remove those ugly require/include things from your code.

    I hope that clarifies - it's confusing because namespaces *seem* to make include/require statements no longer necessary (because in practice, this is true). But in reality, on their own, they just make class names longer and mean more typing.

    Cheers!

  • 2014-06-04 ENetArch

    So, why wasn't the required_once function removed from your example? If that function is required to import your classes, then there is no purpose in updating code to include namespaces, since there is no benefit in reducing code, instead, you've increase code.

    The purpose of adding a namespace, not only has to reduce class name clashes, but also automate the finding and binding of classes somehow, otherwise there is no use to using namespaces.

  • 2014-02-12 Jerome Covington

    That was awesome. Thanks for this. Namespaces and object-oriented code in PHP are bringing me back.

  • 2014-01-23 weaverryan

    Hi there!

    Namespaces and using the include/require statements don't do the same thing - it's one of the trickiest parts of learning namespaces. You still need to include/require any file before using the class inside of it (unless you use an autoloader, like the one Composer gives you). Namespaces have nothing to do with that part.

    The point of namespaces is, basically, to give you a systematic way to make your class names longer. When you have the `Acme\Tools` namespace, the full class name ends up being `Acme\Tools\Foo`. Why is this useful? Well, on its own, it's not :). It's really so that 2 3rd-party library authors an choose 2 different namespaces so that their class names don't conflict. Namespaces really help to serve that purpose: to avoid conflicts between libraries.

    If you want to see a little bit more on the autoloading side of things (i.e. removing the need for require/include) - check out http://knpuniversity.com/scree.... Again, it's actually unrelated to namespaces.

    Cheers!

  • 2014-01-23 spudgun

    You explained what namespaces do, but you didn't explain why I might need them. You say "This is just like referring to a file by its absolute path.", so ... why don't you just do that?

    include('Acme/Tools/Foo.php');

  • 2013-12-08 JC

    Wow... you really did it in 120 secs :-)