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# class_exists

(PHP 4, PHP 5)

class_exists -- Checks if the class has been defined

## Description

bool class_exists ( string class_name [, bool autoload] )

This function returns `TRUE` if the class given by class_name has been defined, `FALSE` otherwise.

Example 1. class_exists() example
`<?php // Check the class exists before trying to use it if (class_exists('MyClass')) { $myclass = new MyClass(); } ?>`

class_exists() will attempt to call __autoload by default, if you don't want class_exists() to call __autoload, you can set the parameter autoload to `FALSE`.

Example 2. autoload parameter example
`<?php function __autoload($class) { include($class . '.php'); // Check to see if 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(); } ?>`

> Note: The autoload parameter was added in PHP 5

See also interface_exists(), and get_declared_classes().

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