Looking at a posting about 5.4 vs 5.3 -
http://www.attackr.com/php-5-4-vs-5-3-difference-what-to-watch-out-for-when-coding-with-new-version/it appears there's an issue with safe mode in 5.4 and I seem to recall from a few years back that we do need safe mode for UBB. Is that still true, or has that changed at some point? That would seem to mean that we'd need to stay on the 5.3 track for now, if I'm remembering properly.