PHP Namespaces | Learn Computer Academy

OOP — Namespaces

As soon as a project has more than a handful of classes — or uses any external package (covered in the Composer lesson ahead) — two classes with the same name is a real risk. A namespace prevents that collision.

Declaring a Namespace

A namespace declaration must be the very first statement in a PHP file.

<?php
namespace App\Models;

class User {
    // this class's full name is App\Models\User
}

Why This Matters

<?php
namespace App\Models;
class User { /* ... */ }

namespace App\Auth;
class User { /* ... */ }   // a completely different class,
                            // fully named App\Auth\User —
                            // no naming conflict at all

Using a Class from Another Namespace — use

<?php
namespace App\Controllers;

use App\Models\User;

$user = new User();   // resolves to App\Models\User

Aliasing with as

Useful when two classes from different namespaces would otherwise share the same short name.

use App\Models\User;
use App\Legacy\User as LegacyUser;

$user = new User();
$oldUser = new LegacyUser();

Namespaces usually mirror folders

The convention followed by nearly every modern PHP project — and the one Composer's autoloading (next lesson) expects — is one namespace matching the folder structure: App\Models\User lives in app/Models/User.php.