On the HHVM blog today there's a new post shows how far along they are with parity with the PHP language based on the tests from a sampling of several large PHP-based projects.

HHVM has a large suite of unit tests that must pass in several build configurations before a commit reaches master. Unfortunately, this test suite passing doesn’t tell you if HHVM can be used for anything useful – so we periodically run the test suites for popular, open source frameworks. [...] The frameworks test page is now public, as is the JSON data backing it (which you’re welcome to use).

They look briefly at what exactly is tested (latest stable version, with exceptions) and how it all works. The tests are run once an hour and are based on a completely clean build of HHVM in "csv" mode. The results of the tests are automatically pushed into the MySQL+Memcached system reporting system, accessible via the JSON API.

On the Facebook HHVM (HipHop VM) blog there's a recent post sharing some of their progress towards parity with the PHP language inside the tool (and the results of their "three week lockdown").

On November 4th, the HHVM team went on a 3-week performance and parity lockdown. The lockdown officially ended on November 22th. Overall, this lockdown was a qualified success. [...] Going into lockdown, the team knew that awesome performance alone would not suffice in making HHVM a viable PHP runtime to be used out in the wild. It actually had to run real, existing PHP code reliably.

In the post they include some numbers from their testing, the pass/fail status of the unit test suites for several major PHP projects including Composer, Joomla, Laravel, Slim and phpMyAdmin (with an overall parity of 98.58%). They share the raw numbers of the results and describe some of the testing environment, including some "assumptions and caveats" about the process. They also contributed back fixes as a part of the work, putting pull requests out there for several projects. They finish the post with some of the performance numbers, noting that they passed their goal and made it to 16% for an instance of facebook.com.

On the HHVM.com blog, there's a post talking about the speed of the HipHop VM (from Facebook) but how it still doesn't support everything built into PHP (and the work being done to bring it up to parity).

HHVM is a highly performant PHP runtime. In fact, it is nearly 40% faster than HPHPc, and only getting faster. [...] Performance is critical, but it isn’t everything. In order to gain broader adoption for HHVM, being able to run popular frameworks is a must; in other words, we can have the highest performing PHP runtime, but if doesn’t run real-world code without a lot of pain, then it won’t be used widely. Understanding this, we are putting serious resources around parity with the PHP runtime.

The post includes a table of features that have been ported and ones currently in the works, based on unit test coverage. They've based it on various well known PHP projects including PHPUnit, Symfony, Laravel, the Facebook SDK and many others. Their initial goal is to allow these frameworks to work 100% of the time inside the HHVM, but to continue the work from there, implementing other PHP features. If you'd like to help out with the process, they also welcome contributions.