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')) {
$myclass = new MyClass();
}
?>
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class_exists() will attempt to call __autoload by
default, if you don't want class_exists() to
call __autoload, you can set the parameter autoload
to FALSE.
Example 2. autoload parameter example
<?php
function __autoload($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();
}
?>
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Note:
The autoload parameter was added in PHP 5
See also interface_exists(), and
get_declared_classes().