output_buffering "0" PHP_INI_PERDIR|PHP_INI_SYSTEM

I wanted to set output_buffering on... 'cause I can't quite get the headers right... and I don't have access to the php.ini. so I was thinking of using ini_set()...

but then it has options PHP_INI_PERDIR|PHP_INI_SYSTEM and as far as I can get it.. I cannot set it in scripts... Is there any other way to do this?