PHP
Multi-level namespaces
Learn the multi-level namespace structure in the Sub\Module\Class form.
Multi-level namespaces
You can split namespaces into sub-levels to build a hierarchy: App\Models\User, App\Services\Auth\Login. Here App is the vendor prefix, Models and Services are sub-levels.
Each \ is a level separator. PHP sees them as a tree: App is the root, Models and Services are branches. This structure keeps large projects organized.
Why is the vendor prefix important?
In the PSR-4 standard the vendor prefix is usually the producer or project name: Symfony\..., Laravel\..., Monolog\.... This prevents namespace clashes between different libraries.
In your own project, picking a unique prefix like App\... or MyCompany\Project\... is a good habit. The more unique the prefix, the lower the clash risk.
Exercise Define a multi-level namespace and class
Define namespace App\Services\Auth;. Add a Login class with public static function attempt($user) that prints the user name with a "Login: " prefix. Then call Login::attempt("Alex") and print __NAMESPACE__.
Show example solution
" . $user . "\n"; } }. Call Login::attempt("Alex"); and echo __NAMESPACE__ . "\n";.
Example solution:
<?php
namespace App\Services\Auth;
class Login {
public static function attempt($user) {
echo "Login: " . $user . "\n";
}
}
Login::attempt("Alex");
echo __NAMESPACE__ . "\n";
Test yourself
-
Complete the multi-level namespace declaration
<?php
____ App\Models\Repository\UserRepository;
$info = ["table" => "users"];
class UserRepository {}
Show answer
<?php
namespace App\Models\Repository\UserRepository;
$info = ["table" => "users"];
class UserRepository {}
-
Match the multi-level namespace concepts
- App
- Vendor prefix
- \
- Level separator
- App\Models\User
- Three-level name
- App\Services\Auth
- Four-level name
-
In App\Models\User, what is App?
- A class name
- The vendor prefix
- A function name
- A variable name
Show answer
The vendor prefix — Correct. App is the vendor prefix; it sets the project's root identity.
Next lesson: PSR-4 autoloading
