Beta Features/PHP7

The Wikimedia Foundation has been employing HHVM to run MediaWiki in production since 2014.[1] Since then, a few things happened that made it compelling for us to move back to the "official" PHP interpreter:

  • PHP 7.x has brought huge performance improvements, so that its performance is nowadays comparable to, if not better than, HHVM for our needs.[2][3]
  • HHVM has dropped support for pure PHP in favour of Hack, an "evolution" of PHP which does not have widespread support.[4]

The Wikimedia Foundation is moving all Wikimedia wikis to use PHP7 in 2019.[5] PHP7 was available as a Beta Feature from January until May 2019.[6]

Replacing the Beta Feature, since March 2019 a percentage of all production traffic has been randomly assigned to use PHP instead of HHVM.

You can verify that it is enabled for you by visiting Special:Version on your wiki, and checking that it says "php" instead of "HHVM" in the "Installed software" table.

Questions and answers


I am a non-technical user. What does this mean?


Hopefully nothing. This is about changing the software used to run the wiki's code. Ideally, you should notice no real difference.

When will this happen?


Work began in 2017 and ramped up over 2018. The beta feature was available from January until May 2019, and PHP 7 support should be production-complete in the first half of 2019.

What should I do if I find an issue?


Report it on Phabricator, in the PHP 7.2 support project.

Why are edits being tagged?


This will help us identify performance, functional, and stability concerns specific to PHP in comparison to HHVM. You can ignore the PHP7 tags.


  1. Giuseppe Lavagetto (December 3, 2014), Wikitech-l All non-api traffic is now served by HHVM Wikimedia Foundation.
  2. Evaluate scalability and performance of PHP7 compared to HHVM Wikimedia Foundation.
  3. Tim Starling (September 20, 2017), Wikitech-l HHVM vs. Zend divergence Wikimedia Foundation.
  4. Max Wang (September 18, 2017), The Future of HHVM HHVM.
  5. Migrate to PHP 7 in WMF production Wikimedia Foundation.
  6. Giuseppe Lavagetto (January 28, 2019), Wikitech-l PHP 7 is now a beta feature Wikimedia Foundation.