I recently did some tweaks and ran across a very interesting issue when hardening PHP using SuHosin. All the WordPress sites stopped working. It seems WordPress needs 256MB in order to work, and by default SuHosin does not specify an upper memory limit.
I was looking for a development server to test builds on and ran across a few pre-made virtual distros that I thought would help. Unfortunately I was not sure of what was installed in some, and most I ran across were Ubuntu, an OS I am not too keen about.