Any sort of automated compiler is certainly going to miss out on a lot of the things that make language X better than PHP though would it not?  And you're still talking about a rewrite of all their PHP code which I'm sure is no small feat.<p>You're also ignoring dependencies and such in the form of PHP modules that would have to be redeveloped for the new language.  Ensuring your front end developers are just as capable in language X(and handle the retraining/learning curve).  Why go through all that trouble when PHP will work just as well for you?