There is pretty much no way 4 to 5 guys could rewrite "www" in another language in parallel to continuing development from a hundred developers, no matter how l

There is pretty much no way 4 to 5 guys could rewrite "www" in another language in parallel to continuing development from a hundred developers, no matter how long they had. However, 4 to 5 guys could write HipHop. What real-world problems do you see staring Facebook in the face in its continued usage of PHP? I'm no PHP fan, but many of the common PHP problems are avoided or mitigated in the code base.