class_alias
get_called_class
Classes/Object Functions
PHP Manual

# class_exists

(PHP 4, PHP 5)

class_exists — Checks if the class has been defined

### Description

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.

### Return Values

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

### Changelog

Version | Description
--- | ---
5.0.2 | No longer returns `TRUE` for defined interfaces. Use interface_exists().
5.0.0 | The `autoload` parameter was added.

### Examples

Example #1 class_exists() example

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

Example #2 `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();
}
?>`

### See Also

- function_exists() - Return TRUE if the given function has been defined
- interface_exists() - Checks if the interface has been defined
- get_declared_classes() - Returns an array with the name of the defined classes

class_alias
get_called_class
Classes/Object Functions
PHP Manual