PHP フレームワークでクラスを自動的にロードするファイル原理の詳細な説明

error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE);
set_include_path($_SERVER['Root_Path'] . '/libs' . PATH_SEPARATOR .
   $_SERVER['Root_Path'] . '/lib' . PATH_SEPARATOR .
   get_include_path() );
if (!function_exists('__autoload')) {
 function __autoload($className)
 {
 ///优化包含路径
 $path=_getRootPath($className);
 $revpath=strtr($className, '_', '/'). '.php';
 $rootpath=$path.$revpath;
 file_exists($rootpath)?include($rootpath):@include($revpath);
 }
}

/**
 *得到根路径*
 */
function _getRootPath($classname)
{
 $pearpath=$_SERVER["PHP_PEAR_PATH"].'/';
 $libpath=$_SERVER['Root_Path'] . '/lib/';
 $libspath=$_SERVER['Root_Path'] . '/libs/';

 if(strpos($classname,'Zend_')===0) return $pearpath; ///zend 框架路径
 if(strpos($classname,'DB_')===0 || strpos($classname,'Interface_')===0 || strpos($classname,'Others_')===0 || strpos($classname,'Pay_')===0 || strpos($classname,'PHPMailer_')===0 ) return $libspath;
 return $libpath;
}