Namespaces

In PHP, namespaces are a way to encapsulate items like classes, interfaces, enumerations, traits, functions, and constants, preventing naming conflicts between different parts of a program. They help organize and structure code, especially in larger projects where multiple developers may be contributing.

<?php

namespace a {
    class x {
    }
}

namespace b {
    // a second class x, although distinct from the previous one
    class x {
    }
}

?>

Documentation

See also Understanding PHP Namespaces: Organising Your Code

Related : Use Alias, Fully Qualified Name

Added in PHP 5.3