HipHop for PHP is a source code transformer for PHP script code. HipHop pro-grammatically transforms PHP source code into C++ and then uses g++ to compile it to machine code. HipHop includes a code transformer, a reimplementation of PHP's run-time system, and a rewrite of many common PHP Extensions to take advantage of these performance optimizations.
HipHop for PHP can substantially increase the speed of PHP applications. Improvements of web page generation throughput by factors of 2 to 6 have been observed.
The sad side is, it is currently works on Linux and FreeBSD. There is no OS X support :(