When using the web installer, I get the warning as part of the Environmental checks:
Warning: Could not find APCu, XCache or WinCache.
There is not a APCu package for PHP7, and I understand that PHP7 has a built in cache that means APCu would no longer be useful. If this is the case, can we detect PHP7 and remove the warning?
I understand that PHP7 has a built in cache that means APCu would no longer be useful.
APC used to be a package providing two features:
As of PHP7, opcode caching is a built-in feature and the key/value storage package is now known as APCu. The MediaWiki environmental check is about the key/value storage feature, not the compilation cache. As such, the warning you got seems to be working as intended.
See also https://www.mediawiki.org/wiki/Manual:Performance_tuning.
http://packages.ubuntu.com/xenial/php-apcu
As above, opcode cache is a seperate component now, ala http://packages.ubuntu.com/xenial/php7.0-opcache
I should note MW had some issues handling apcu, but this was fixed in T140587 and T140961, and backported to REL1_27, so will be out in the next point release
Is there anything to actually do here?
Nope, I think this was just a misunderstanding. @Jjanes Please let us know if there's anything else. Feel free to re-open :)