According to Facebook senior server engineer Haiping Zhao, HipHop, while not fully mature, has cut the social networking giant's CPU usage by half.
"The project has had a tremendous impact on Facebook," Zhao said. "We feel the web at large can benefit from HipHop, so we are releasing it as open source … in hope that it brings a new focus toward scaling large, complex [websites] with PHP."
Zhao says that HipHop is not a compiler, but a code transformer that reworks the PHP runtime, along with a rewrite of extensions to optimize performance.
"HipHop programmatically transforms your PHP source code into highly optimized C++ and then uses g++ to compile it," Zhao said. "HipHop executes the source code in a semantically equivalent manner and sacrifices some rarely used features — such as eval() — in exchange for improved performance."
While PHP offers many developmental benefits, CPU efficiency and memory usage have always been issues.
"Because of this, it's been challenging to scale Facebook to over 400 billion PHP-based page views every month," Zhao said, noting that HipHop allows developers to enjoy the benefits of PHP along with the performance of C++.
You can learn more about what HipHop can do for your at the Facebook Developer's Blog.