I'm setting up my computer again for developing websites. Logically it seems sensible to exactly mirror the version of PHP on the final web server, to help with testing. But it seems kind of nice to use PHP5 and I've already installed Xampp, which has PHP5. When writing my PHP code, how likely am I to write something that will work on PHP5 but not work properly when I transport it over (I'm not talking about involved OO stuff, I know that has changed).
