I mentioned the other day that Facebook was about to open source a method for speeding up PHP. Today they announced HipHop a code transformation tool that converts PHP into C++ and compiles using g++. There is apparently a server component to this strategy as well.
I’m slightly skeptical that this approach will have much more success than the other attempts in the past. This approach may make sense for Facebook, but I don’t think it will pay off for most smaller (relatively speaking) sites.
I think for most users doing something similar to the Unladen Swallow, an effort for Python which is trying to build a custom virtual machine with a JIT built on top of LLVM would be best. Perhaps even Nanojit could be a potential option.
I suspect HipHop will be a fork more than anything else. Regardless it’s a pretty cool project and some really interesting technology.