public static function isReadable($filename)
     {
         if (!$fh = @fopen($filename, 'r', true)) {
             return false;
         }

 public static function autoload($class)
     {
         try {
             self::loadClass($class);
             return $class;
         } catch (Exception $e) {
             return false;
         }
     }

 public static function registerAutoload($class = 'Zend_Loader', $enabled = true)
     {
         if (!function_exists('spl_autoload_register')) {
             require_once 'Zend/Exception.php';
             throw new Zend_Exception('spl_autoload does not exist in this PHP installation');
         }