Fully Qualified Name

A fully qualified name, or a fully qualified class name, is a unique identifier for the PHP name of a constant, class, trait, interface, enum or function : it includes its namespace name.

PHP names may be fully qualified, unqualified or relative.

<?php

namespace A {
    const B = 1;

    function foo() {
        // This is a local name : the namespace A is optional.
        // The fully qualified name is \A\B;
        echo B;

        // This is a fully qualified name
        echo \A\B;
    }
}
?>

Documentation

Related : Use, Namespaces

Added in PHP 5.3