Do NOT upgrade your PHP, especially on a Distro install. You will run into the same problem. The Zend Loader version is for 5.3 which means you will have to update your Zend Loader and the commercial modules will not work.
There's a reason why the install pages in the wiki don't support commercial modules on anything but CentOS 6.x because CentOS 6.x PHP's package it 5.3 and the others are more current versions.