After what felt like years of debate over the notation to use for PHP's namespaces, it seems like the feature itself has had relatively little use or attention since it was actually implemented in PHP 5.3. We're all used to working without it but using it does make code neater.

Take this example (in a file called namespaced-class.php)

namespace Christmas\DaysOf;  

class PartridgeInAPearTree{
}

Now we have a few ways to access that class.

Refer Namespace and Class Name

The simplest way to access a class inside a namespace is simply to prefix the classname with its namespace(s):

include 'namespaced-class.php';

$bird1 = new Christmas\DaysOf\PartridgeInAPearTree();
var_dump($bird1); 

You can use this anywhere in your code.

Import the Namespace

In PHP we can import namespaces using the use keyword, and then just use the last part of the name in place of the namespace. In my contrived Christmas-related example, we'd end up with something that looks like this:

include 'namespaced-class.php';
use Christmas\DaysOf;

$bird2 = new DaysOf\PartridgeInAPearTree();
var_dump($bird2);

This example works well because it saves us from typing anything but the last element of a potentially quite long-winded path.

Alias the Namespace and/or Class

We can alias just the namespace, as shown above, or right down to the class name, using the use keyword. Optionally we can also rename what we'd like to call it, rather than the final element in the path, by using the as keyword.

include 'namespaced-class.php';
use Christmas\DaysOf\PartridgeInAPearTree as Bird;            

$bird3 = new Bird();
var_dump($bird3);
 

Even better, we can give a "nickname" to our namespace, either to avoid clashes or just to give us something more memorable or descriptive to use within the class. This will also be a great trick to use when namespace-using applications become legacy and we have to handle renaming of namespaces.

So Many Options

All of the above examples give a debug output of the same class; the class that was declared in the opening example file and included elsewhere. One thing I noted which was unfamiliar is that you must declare a namespace as the first thing in a file, and that the namespace is implicitly ended at the end of the file.

Are you using namespaces in your applications? How have you implemented them? I'm interested to hear how others are applying these techniques inside their architectures, please share!