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Hacking Up HipHop
One night at a Hackathon a few years ago (see Prime Time Hack), I started my first piece of code transforming PHP into C++. The languages are fairly similar syntactically and C++ drastically outperforms PHP when it comes to both CPU and memory usage. Even PHP itself is written in C. We knew that it was impossible to successfully rewrite an entire codebase of this size by hand, but wondered what would happen if we built a system to do it programmatically.
Finding new ways to improve PHP performance isn't a new concept. At run time the Zend Engine turns your PHP source into opcodes which are then run through the Zend Virtual Machine. Open source projects such as APC and eAccelerator cache this output and are used by the majority of PHP powered websites. There's also Zend Server, a commercial product which makes PHP faster via opcode optimization and caching. Instead, we were thinking about transforming PHP source directly into C++ which can then be turned into native machine code. Even compiling PHP isn't a new idea, open source projects like Roadsend and phc compile PHP to C, Quercus compiles PHP to Java, and Phalanger compiles PHP to .Net.
Needless to say, it took longer than that single Hackathon. Eight months later, I had enough code to demonstrate it is indeed possible to run faster with compiled code. We quickly added Iain Proctor and Minghui Yang to the team to speed up the pace of the project. We spent the next ten months finishing up all the coding and the following six months testing on production servers. We are proud to say that at this point, we are serving over 90% of our Web traffic using HipHop, all only six months after deployment.
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