Facebook Releases HHVM 4.0 With PHP No Longer Supported

HHVM, formerly known as the HipHop Virtual Machine and what was born at Facebook as a higher-performance PHP implementation only to shift focus to running their own PHP-derived Hack programming language, has reached version 4.0 as it officially no longer supports PHP.

HHVM 4.0 doesn't drop support for executing PHP scripts entirely, which will likely happen in their next release when dropping the PHP tag. But in this release already they have removed functionality from PHP arrays that are not present in Hack arrays, deprecation of references, and dropping functions that inspect or alter the caller frame.

Facebook dropping the long-standing PHP support in HHVM shouldn't come as a surprise. Since PHP7 with its much higher performance interpreter upstream, HHVM developers haven't been working on PHP7 compatibility but instead furthering along their own Hack programming language that is now widely used within the confines of Facebook. PHP 7.x meanwhile is in much better performance standing than during the PHP5 days when HHVM was much faster. They've been on the path for a while to drop PHP support and with HHVM 4.0 that goal is being realized.

HHVM 4.0 also now prefers developers postfix their code with a .hack file extension, their regex namespace is no longer considered experimental, return-by-reference support is removed, and a variety of other changes as a result of their slow-moving removal of PHP-specific features.

More details on HHVM 4.0 can be found via HHVM.com. HHVM 4.1 will be their next time-based feature release due out in about eight weeks but following that point they plan to move to a weekly release cadence for HHVM.