If we're going that route, the fastest php performance you would probably get from facebook's HHVM JIT compiling php engine: https://github.com/facebook/hiphop-php

It's no accident that zend optimizer (bytecode cache) is being bundled into php 5.5 as open source, as mere bytecode caching is now not fast enough to charge money for when hhvm is open source. I expect the next version of zend's commercial php server product to contain a JIT engine to match what hhvm can do.

That would certainly be very interesting, especially as PHP is being nudged into that area (Twig also now offers a c-module).

I really hope the author picks up on this and compares it. It could provide some tremendous insights into pushing PHP further into this space.