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[edit]

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

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?[edit]

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?[edit]

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

Why are edits being tagged?[edit]

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.