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We all know that the name of this class is BattleManager. When we want to use it, we reference BattleManager. No matter what we do - static or non-static - if we want to work with this class we call it by its name, BattleManager. Simple.

Why am I pointing out the painfully obvious? Because we're about to make this class name longer, but maybe not how you'd expect. We're going to use a namespace.

Let's see some Namespaces

At first, why namespaces exist might not be obvious, so hold onto that question. Let's see how they work first.

Above any class, you can - if you want to - add a namespace keyword followed by some string. Like, Battle or something more complicated like Battle\HiGuys\NiceNameSpace. A namespace is a string, and you can give it different parts by separating each with a backslash \ - that's the slash that feels a little wrong when you type it - it's usually an escape character.

To keep things simple, just set the namespace to Battle for now:

94 lines lib/Service/BattleManager.php
... lines 1 - 2
namespace Battle;
class BattleManager
... lines 6 - 94

As soon as we did that, we actually changed the name of this class: it is no longer called BattleManager. In fact, you can see that PhpStorm now highlights our code with an "Undefined class BattleManager" error. Thanks to the namespace, the class is now called Battle\BattleManager:

140 lines index.php
... lines 1 - 11
$battleTypes = Battle\BattleManager::getAllBattleTypesWithDescriptions();
... lines 13 - 140

Refresh to prove it. Great!

So... that's really it! When you add a namespace above a class, the full class name becomes that namespace, a \, and then class name. Every place we reference this class name will now need to change - like inside of Container. We'll do that in a few minutes - we've got a few other things to do first.

So Why do Namespaces Exist?

Now that you know how namespaces work, you're probably wondering, why do these even exist? How does this help me in my coding? Well, the short answer is... it doesn't help you. In fact, namespaces weren't meant to help you - they were meant to help external library developers. So I guess, if you're one of those it does help.

In a nut shell, as you go further into development, you'll start to use a lot of 3rd-party, libraries written by other people. That's cool because those libraries will give us new classes to help solve problems.

The reason that namespaces exist is to avoid collisions in those external libraries. Imagine we're using library A and library B, but that they both have a class called Battle. Without namespaces, we'd be lost in space: we wouldn't be able to use both libraries. But if each library has a unique namespace, we won't collide: they'll simply be called something like LibraryA\Battle and LibraryB\Battle.

This means that namespaces do help us, but only indirectly. When we're working with namespaces it just makes our class names longer.

The use Statement

There is one other thing that you need to know with namespace: it's the mystical use statement.

When you want to reference a class, it's perfectly valid to type out the entire long class name right where you need to use it. But in practice, you won't see this very often. Instead, people typically add a use statement at the top of the file that references the full class name: Battle\BattleManager:

143 lines index.php
... lines 1 - 2
use Battle\BattleManager;
... lines 4 - 143

As soon as you do, when you need to work with the class, you can once again write out only the short class name:

143 lines index.php
... lines 1 - 2
use Battle\BattleManager;
... lines 4 - 14
$battleTypes = BattleManager::getAllBattleTypesWithDescriptions();
... lines 16 - 143

And while you'll only have one namespace per file, you'll have as many use statements as you need.

To be clear, the use statement does not change how namespaces work: it's just a shortcut. When PHP executes this file, it sees class BattleManager and says:

Huh, BattleManager? Let me check all of the use statements at the top of this file.

PHP then looks to see if any of the use statements end in the word BattleManager. If it finds one, it basically copies the long class name and pastes it below right before executing the file. What I just did manually is what PHP basically does at run-time.

So use statements are just this nice, extra feature. And technically, you could avoid using them and instead write-out full class names right where you need them.

Ok! We're going to do a lot more with namespaces. But first, we need to turn to a very related topic called autoloading.

Go Deeper!

If you still have questions about namespaces - check out our short course PHP Namespaces in 120 Seconds or just leave a comment.

Leave a comment!

  • 2017-04-05 Diego Aguiar

    Hey Brian!

    Nice catch! that's definetely a mistake from our part, that should be a semicolon as you said, we will fix it as soon as we can

    Have a nice day!

  • 2017-04-05 Brian Morris

    In challenge #4, the code example in the question contains:
    namespace Model\Planet.
    Should that be a semicolon instead of a period?

  • 2016-08-29 Victor Bocharsky

    Hey Syed,

    Thanks for this report! Yes, it's the same. You need to use a full namespace of a class or you could add a use statement for the class and then use its class name. You'll find more info about use statement in this and More Fun with use Statements next chapter. Actually, it was a one more subtask you should solve in that challenge.

    Cheers!

  • 2016-08-27 Syed

    Hi!

    I noticed the solution to challenge #1 on this video is incorrect. The RandomlyColoredPlanet implements PlanetInterface but of course PHP is looking for that interface in the namespace 'Model\Planet' and can't find it.

    So, it needs to be:

    namespace Model\Planet;

    class RandomlyColoredPlanet implements \PlanetInterface

    I would have created a pull request on github for this but couldn't find where the challenge code was kept.

    Edit:

    Looking more closely it looks like a use PlanetInterface was used at the top of the class. Assuming this works the same as above?