PHP not fully working

[shaggy]

Hi all,

I have a problem, PHP is working fine on the ispCP domain (admin.domain.tld) but it's not working for anything else, I install OmegaBill, and it just shows a blank white page. a customer uploaded the site to the new server and it's also showing blank white pages, I have looked in all logfiles in /var/logs and can not find anything todo with my issue, I done grep domain.tld-combined.log and open the problem page and nothing is registered in there. is there another log file for PHP Errors somewhere else on the server? and how can I fix my issue?