Introduction to Namespaces

Part of the Object Oriented Programming section of Coddy's PHP journey — lesson 10 of 91.

As your PHP projects grow, you'll create many classes. What happens when two classes have the same name?

For example, you might have a User class for your blog and another User class for your shop. Namespaces solve this problem by organizing classes into logical groups.

A namespace is like a folder for your classes. You declare it at the top of your PHP file using the namespace keyword:

<?php
namespace Blog;

class User {
    public $name;
    
    public function __construct($name) {
        $this->name = $name;
    }
}

Now you can have another User class in a different namespace:

<?php
namespace Shop;

class User {
    public $email;
    
    public function __construct($email) {
        $this->email = $email;
    }
}

To use a namespaced class, you reference it with its full path using a backslash:

<?php
$blogUser = new \Blog\User("Alice");
$shopUser = new \Shop\User("alice@example.com");

echo $blogUser->name . "\n";
echo $shopUser->email . "\n";

Output:

Alice
alice@example.com

The backslash \ separates namespace levels, similar to how slashes separate folders in a file path. You can also create nested namespaces like App\Models\Blog for deeper organization.

Key Point: Namespaces prevent naming conflicts and keep your code organized. Always declare the namespace before any other code in your file (except for declare statements).

Challenge

Easy

Let's organize a small application using namespaces to prevent naming conflicts between classes with the same name.

Imagine you're building a system that handles both vehicles and animals. Both domains have an entity called Car — one represents an actual automobile, while the other is a pet cat named "Car" (yes, some people name their cats that way!).

You'll create three files:

Vehicle/Car.php — Define a Car class in the Vehicle namespace with a public $brand property. The constructor should accept the brand name and set it. Add a describe() method that returns "Vehicle: [brand]".
Animal/Car.php — Define a Car class in the Animal namespace (this is a cat named Car!). It should have a public $age property. The constructor accepts the age and sets it. Add a describe() method that returns "Cat named Car, age: [age]".
main.php — Include both class files using require_once. Create one object from each namespace using their full namespace paths, then print the result of calling describe() on each object (each on its own line).

In main.php, create:

A Vehicle\Car with brand "Toyota"
An Animal\Car with age 3

Remember to use the backslash \ to reference namespaced classes with their full path when creating objects.

Cheat sheet

Namespaces organize classes into logical groups and prevent naming conflicts when multiple classes share the same name.

Declare a namespace at the top of a PHP file using the namespace keyword:

<?php
namespace Blog;

class User {
    public $name;
    
    public function __construct($name) {
        $this->name = $name;
    }
}

You can have classes with the same name in different namespaces:

<?php
namespace Shop;

class User {
    public $email;
    
    public function __construct($email) {
        $this->email = $email;
    }
}

To use a namespaced class, reference it with its full path using a backslash \:

<?php
$blogUser = new \Blog\User("Alice");
$shopUser = new \Shop\User("alice@example.com");

echo $blogUser->name . "\n";
echo $shopUser->email . "\n";

The backslash separates namespace levels, similar to folder paths. You can create nested namespaces like App\Models\Blog.

Important: Always declare the namespace before any other code in your file (except declare statements).

Try it yourself

<?php
// Include the class files
require_once 'Vehicle/Car.php';
require_once 'Animal/Car.php';

// TODO: Create a Vehicle\Car object with brand "Toyota"
// Remember to use the full namespace path with backslash

// TODO: Create an Animal\Car object with age 3
// Remember to use the full namespace path with backslash

// TODO: Print the result of describe() for each object (each on its own line)

?>