Hm, I possibly need to clarify it up a bit. Now, as far as I understand it the Zend backend takes the PHP code, creates opcodes and executes it in a VM, wherea

Hm, I possibly need to clarify it up a bit. Now, as far as I understand it the Zend backend takes the PHP code, creates opcodes and executes it in a VM, whereas HipHop takes the code, compiles it down to C++, compiles it again with G++ then runs the resulting C++ binary instead. To me at that stage HipHop is no longer a backend, but an entire build system transforming the language away from PHP. Like I said, I'm not as intimately familiar with the system, but I thought it was along the lines of they have a dynamic system for local development, and when they serve it up it's run through the HipHop compile process.