Beta Features/PHP7

The Wikimedia Foundation has been employing HHVM to run MediaWiki in production since 2014. 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, if not better, than HHVM for our needs.
 * HHVM has dropped support for pure PHP in favour of Hack, an "evolution" of PHP which doesn't have widespread support.

The Wikimedia Foundation is moving all Wikimedia wikis to use PHP7 in early 2019 PHP7 will be available from January 2019.

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

 * When will this happen?
 * Work began in 2017, ramped up over 2018, and should be production-complete in the first half of 2019.
 * What should I do if I find an issue?
 * Report it
 * 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 them.