> different php versions

How do you do that one? Last time I tried (granted, a long time ago), apache-mod-php was hardcoded into a single php version, and you couldn't have different versions of it on apache either.

I always classified php as one of the most problematic languages that need containment. There's not only that hard dependency on the version, but the language also has a global configuration storage that, last time I used it, can not be overloaded.