Portability concerns

Hi Not sure if this is the right forum for this question, but I'll give it a shot and hope that someone will redirect me if I'm in the wrong place. Lately I've been thinking about how to write portable PHP code, and the most important settings that can break scripts are register_globals, magic_quotes and the error level. So I develop with register_globals off, put in checks for magic_quotes, and use E_ALL. But what other issues are there? Should there not be a part of the PHP documentation dedicated to describing all the things you should worry about if you want to write portable code? Shouldn't there be a "portability standard" for PHP, or is there allready one? I'm sure there must be other things to consider than the three features/settings I have mentioned, and getting a good overview/reference for these would be a boon to everyone trying to write portable code. This also cover coding practices, like using relative paths and urls rather than static ones, maybe even using abstraction layers on top of the DB (if using one). André Næss