php中使用__autoload()自动加载未定义类的实现代码

<?php
/**
* 自动加载相关类库文件
*/
function __autoload($classname){
if(substr($classname,-6)=="Action"){
include APP_PATH.'controllers/'.$classname.'.class.php';
}elseif(substr($classname, -5)=="Model"){
include APP_PATH.'models/'.$classname.'.class.php';
}elseif($classname=="Smarty"){
include SYSTEM_PATH.'smarty/Smarty.class.php';
}else{
include APP_PATH.'common/'.$classname.'.class.php';
}
}
?>

<?php
function __autoload($class_name) {
$path = str_replace('_', DIRECTORY_SEPARATOR, $class_name);
require_once $path.'.php';
}
?>