PHPBB3進入管理後台發生403的錯誤

我的PHPBB3是裝在ServerZoo上面，發現剛裝好要進入ACP管理後台出現下列訊息

Forbidden

You don't have permission to access /phpBB3/adm/index.php on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.


解決方式如下:
修改\adm\index.php
1.找到 $phpbb_root_path = (defined('PHPBB_ROOT_PATH')) ? PHPBB_ROOT_PATH : './../';
2.換成 $phpbb_root_path = (defined('PHPBB_ROOT_PATH')) ? PHPBB_ROOT_PATH : '../';
3.儲存，搞定!!