Most of Titan's web stuff was in PHP and JavaScript (specifically, jQuery) before I left. Don't know how much that has/will change, so there is that caveat.
Just remember, PHP is a popular language, mostly because it lets you do damn near anything. Be advised, though, that because of that ability, it is very easy to write code that, while functional, is very hard to read or understand unless you are absolutely the exact state of mind as when you originally wrote it.