Given that in the conventional PHP interpreter, everything is executed from scratch on each request, I wonder how the JIT behaves here, especially since most PHP programs live and die in less time than it seems to take the Pypy JIT to warm up. If/when a version with the web side of the stack is implemented, will JITed code survive across requests?
As mentioned, there is the opcode cache. I'm also thinking about FastCGI setups, where PHP is running the whole time, just waiting to execute code requests.