private static function checkUpfilePath()
 {
     self::$filepath = rtrim(self::$filepath, '/') . '/';
     if (!file_exists(self::$filepath)) {
         if (!mkdir(self::$filepath, 0755, TRUE)) {
             self::error(-2);
             return FALSE;
         }
     }
     if (!is_writable(self::$filepath)) {
         self::error(-1);
         return FALSE;
     }
     return TRUE;
 }