Thanks to some fantastic work by Erik Bernhardson[0], MediaWiki-Vagrant can now run MediaWiki on HHVM. The setup runs HHVM behind Apache using FastCGI, which is a close match to how we think we'll be running it in production. It uses the 'hhvm-nightly' packages from Facebook, so you can test MediaWiki core and extensions against cutting-edge builds.
To switch MediaWiki from PHP to HHVM, simply run 'vagrant enable-role hhvm', followed by 'vagrant provision'. To switch back to PHP, run 'vagrant disable-role hhvm' and reprovision.
Please try it out and FILE BUGS for any issues you encounter. This includes not only provisioning failures (which should be reported under the MediaWiki-Vagrant product in Bugzilla) but also any instances of PHP code breaking under HHVM. There is now an 'hhvm' keyword in Bugzilla you can use to tag your report.
Three cheers for Erik B., and for Facebook's Paul Tarjan, whose recent packaging work makes this possible.
[0]: https://gerrit.wikimedia.org/r/#/c/105834/
--- Ori Livneh ori@wikimedia.org