Firstly, I must admit that I don't know much about setting up PHP beyond the basics. I have an Ubuntu 10.04 server system (hosted) running primarily as an FTP store for a commercial store software. The server that the commercial store is installed on is unfortunately not very reliable, and would like to move that to this Ubuntu 10.04 server. (We've already received permission from the store vendor to do this.) My problem is that they use Zend optimizer which is only compatible with PHP 5.2. I have tried a couple of "hacks" to downgrade PHP to 5.2, but it breaks so many other things that it doesn't seem worth it.
My idea is to install some sort of container of Ubuntu 8.04 (like OpenVZ) on the server to house a native install of PHP 5.2 to meet the dependency of the store software. However, it appears that OpenVZ is no longer supported on Ubuntu. Is there another solution similar that I could run on a hosted server to installed a separate "container-like" 8.04 system?
If you want to stick to something that is supported on Ubuntu you could use KVM.