I didn't say that they don't write it, I said that they don't actually run it. :...

eurleif · on Oct 10, 2011

By that logic, they don't run C++ either; they run machine code. So does everyone else.

jrockway · on Oct 10, 2011

But to be fair, their PHP is a subset of the official PHP, and they probably use all of their own libraries (rather than the ones you have access to outside of Facebook).

So if you want Facebook to be your PHP success story, all you get out of it is "PHP didn't kill their company; they were eventually able to move away", which I suppose is not exactly a swimming endorsement.