class_exists

(PHP 4, PHP 5, PHP 7)

Checks if the class has been defined

bool class_exists ( string $class_name [, bool $autoload = true ] )

This function checks whether or not the given class has been defined.

Parameters:

class_name

The class name. The name is matched in a case-insensitive manner.

autoload

Whether or not to call __autoload by default.

Returns:

Returns TRUE if class_name is a defined class, FALSE otherwise.

Changelog:

5.0.2

No longer returns TRUE for defined interfaces. Use interface_exists().

Examples:

class_exists() example

<?php
// Check that the class exists before trying to use it
if (class_exists('MyClass')) {
    $myclass = new MyClass();
}

?>

autoload parameter example

<?php
function __autoload($class)
{
    include($class . '.php');

    // Check to see whether the include declared the class
    if (!class_exists($class, false)) {
        trigger_error("Unable to load class: $class", E_USER_WARNING);
    }
}

if (class_exists('MyClass')) {
    $myclass = new MyClass();
}

?>