I'd guess that whoever downvoted you thought this was a troll meant to start a flamewar with C++ vs. PHP and whether one or the other is more difficult (read "better" or "a real language").

It's interesting to note though, that Facebook does uses PHP and C++ extensively. And Facebook maintains a large a number of open source PHP and C++ projects. So I suppose that some Facebook engineers are more involved with PHP and some more involved with C++.

But more importantly, I don't think Facebook engineers are bound to a technology. They think about how to solve problems. If PHP is the best tool to solve a problem, they'll use that. If it's C++, they'll use that instead.

Ah I hadn't thought of that about the flamewar. I use both languages (now mainly C++ as I don't need to use PHP for the stuff I am writing anymore).

You're right about them using the right tool for the job - their entire HipHop etc. (whatever it is called now) creations to convert PHP to C++ and run a C++ web server are a good indication of this. Good point!