We have PHPCS setup now in https://gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/633045, with some issues fixed so far. There's still much more left though. Let's work on enabling all of these.
- [ ] Control structure sniffs: https://gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/633305
- [ ] Forbidden function sniffs: https://gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/633302
- [ ] Generic standard sniffs
- [ ] MediaWiki sniffs
- [ ] MediaWiki: function comment sniffs
- [ ] MediaWiki: naming convention sniff
- [x] MediaWiki: use statements sniffs: https://gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/633050
- [ ] MediaWiki whitespace sniffs
- [x] PSR sniffs
- [x] PSR-2 sniffs: https://gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/633051
- [x] PSR-12 sniffs: https://gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/633289
- [ ] Squiz standard sniffs
- [x] Self member references: https://gerrit.wikimedia.org/r/c/mediawiki/skins/Cosmos/+/633290
- [ ] Argument spacing in function declarations
- [ ] Visibility scope
- [ ] General whitespace