As a benchmark for their progress over the past three weeks of development to improve their open-source PHP interpreter, HHVM now passes about 99% of the unit tests from 21 popular open-source frameworks. HipHop developers also achieved a ~15% performance improvement across the board for their PHP interpreter that runs all the PHP code at Facebook.com.
The HipHop Virtual Machine has long been very fast and with nearly every update they make PHP on HHVM even faster. After this three-week lock-down, more PHP code runs on the HipHop Virtual Machine and it's doing so while boasting yet another large speed improvement. HHVM is becoming an increasingly viable alternative to the upstream PHP interpreter for production workloads outside of Facebook. The Phoronix Test Suite is HHVM-compatible and in my development work using HHVM it's been a great experience. The Anzwix back-end and some other projects of mine are also riding happily atop HHVM.
For those interested in all of the details about the latest round of HHVM improvements, see the project's blog post. The Facebook HHVM team has also committed to further major improvements in 2014. The code for this JIT compiler that's put out under the PHP/Zend licenses can be found on GitHub.