PHP Namespaces

PHP namespaces are a way to organize and group related classes, interfaces, functions, and constants. They help prevent naming conflicts and improve code organization in large projects.

Why Use Namespaces?

Namespaces solve the problem of name collisions between code you create and internal PHP classes/functions or third-party classes/functions. They allow you to:

• Group related classes
• Avoid naming conflicts
• Improve code readability
• Create aliases for long class names

Declaring Namespaces

To declare a namespace, use the namespace keyword at the top of your PHP file:

namespace MyProject\SubNamespace;

class MyClass {
    // Class implementation
}
    

Using Namespaced Classes

To use a class from a namespace, you can either use the fully qualified name or import it with the use statement:

// Using fully qualified name
$obj = new \MyProject\SubNamespace\MyClass();

// Importing the class
use MyProject\SubNamespace\MyClass;
$obj = new MyClass();
    

Namespace Aliases

You can create aliases for namespaces or classes using the use keyword with as:

use MyProject\SubNamespace\MyClass as MC;
$obj = new MC();
    

Global Namespace

To reference a class or function in the global namespace, use a leading backslash:

namespace MyProject;

$obj = new \stdClass(); // Refers to the global stdClass
    

Best Practices

• Use PSR-4 autoloading standard for namespace and directory structure
• Keep one class per file
• Name your namespaces after your project or package name
• Use meaningful and descriptive names for namespaces

Related Concepts

To fully understand and utilize PHP namespaces, you should also be familiar with:

• PHP OOP Introduction
• PHP Classes and Objects
• PHP Autoloading

By mastering PHP namespaces, you'll be able to write more organized, maintainable, and scalable code. They are especially useful in large projects or when working with multiple libraries.