未找到“PDO”类 - 已安装PDO驱动程序

on my server, PDO drivers are installed.

http://randani.com/test.php

but on my sub-domain I got this error message:

 Symfony \ Component \ Debug \ Exception \ FatalErrorException (E_UNKNOWN)
Class 'PDO' not found

my sub-domain:

http://dev.randani.com/

where is my wrong?