Facebook started with PHP - but quickly replaced the standard library, the interpreter, and then eventually the language itself (Hack still looks kind-of-like PHP, but is no longer compatible)
(Working with both vanilla PHP and Hack; I find the latter orders of magnitude nicer to work with - just for XHP alone, I wish I could switch my PHP projects to be Hack projects...)
(Working with both vanilla PHP and Hack; I find the latter orders of magnitude nicer to work with - just for XHP alone, I wish I could switch my PHP projects to be Hack projects...)