Scaling PHP : HipHop and Quercus
While PHP is very popular, it unfortunately doesn't perform as some of its competitors. One of the ways to make things faster is to write PHP Extensions in C++. In this post we will describe two different ways developers can solve this problem and the milage you might get from either model may vary.
Since Facebook is mostly running PHP, it noticed this problem pretty early, but instead of asking its developers to move from PHP to C++ one of their developers hacked up a solution to transform PHP code into C++.
Yesterday, Facebook announced they are opening up HipHop, a source code transformer, which changes PHP code into a more optimized C++ code and uses g++ to compile it. With some minor sacrifices (no eval support) they noticed they were able to get 50% performance improvement. And since they serve 400 billion page views every month, that kind of saving can free up a lot of servers.
More info on HipHop
Quercus on the other hand is a 100% java implementation of PHP 5. What makes this more interesting is that Quercus can now run in Google App Engine pretty much the same way JSPs can.
Cauchoâ€™s Quercus presents a new mixed Java/PHP approach to web applications and services where Java and PHP tightly integrate with each other. PHP applications can choose to use Java libraries and technologies like JMS, EJB, SOA frameworks, Hibernate, and Spring. This revolutionary capability is made possible because 1) PHP code is interpreted/compiled into Java and 2) Quercus and its libraries are written entirely in Java. This architecture allows PHP applications and Java libraries to talk directly with one another at the program level. To facilitate this new Java/PHP architecture, Quercus provides and API and interface to expose Java libraries to PHP.
The demo of Quercus running on GAE was very impressive. Any pure PHP code which doesnâ€™t need to interact with external services would work beautifully without any issues on GAE. But the absence of Mysql in GAE means SQL queries have to be mapped to datastore (bigtable) which might require a major rewrite to parts of the application. But its not impossible, as they have shown by making wordpress run on GAE (crawl might be a better word though).
While Quercus is opensource and is as fast as regular PHP code in interpreted mode, the compiler which is way faster is not free. Regardless Quercus is a step in the right direction, and I sincerely hope PHP support on GAE is here to stay.