(PHP 4, PHP 5)class_exists -- 检查类是否已定义
bool class_exists ( string class_name [, bool autoload] )
如果由 class_name 所指的类已经定义，此函数返回 TRUE，否则返回 FALSE。
<?php
// Check the class exists before trying to use it
if (class_exists('MyClass')) {
$myclass = new MyClass();
}
?>
<?php
function __autoload($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();
}
?>