怎么自动加载类文件

如何自动加载类文件！
现在用的是autoload（代码如下：），还有别的方法能自动加载类文件吗？除了include（具体文件路径）

PHP code

function __autoload($className){if(file_exists('model/'.$className.'.class.php')){include_once('model/'.$className.'.class.php');}if(file_exists('Controller/'.$className.'.class.php')){include_once('Controller/'.$className.'.class.php');}$prefix=$GLOBALS['groupName']=='main'?'':'../';if(file_exists($prefix.'core/'.$className.'.class.php')){include_once($prefix.'core/'.$className.'.class.php');}if(file_exists($prefix.'core/Smarty-3.1.6/'.$className.'.class.php')){include_once($prefix.'core/Smarty-3.1.6/'.$className.'.class.php');}if(file_exists($prefix.'core/Smarty-3.1.6/sysplugins/'.$className.'.php')){include_once($prefix.'core/Smarty-3.1.6/sysplugins/'.$className.'.php');}}

PHP code

$arr = array('classPath1','classPath2','classPath3');foreach($arr as $v){  $new_path = $v.$className.'.php';  if(file_exists($new_path)){    include_once($new_path);    break;  }}