Explicitly check for code style compliance against some standard at PR time

[gregcorbett]

It's not clear to me what codacy and codeclimate are actually using as "the gold standard" of PHP code. Specifying a well known code standard is at least possible in codeclimate.

We also have a PHP Mess Detector config ruleset around (#265), and I like the fact we can use that to configure exceptions for things we are never going to change (variable names like $em for example). But with phpcodesniffer it seems we can aim for a standard, even if it tells us "the code is bad and you should feel bad" all the time. Perhaps another PHP linter / CI platform can do both.

PSR-12: Extended Coding Style is a standard. Other standards may be available.

[tofu-rocketry]

#265 has now been merged to give a basic PHP Mess Detector rule set.

PSR-12 seems like a good standard to aim for as a baseline, as it's used by a number of large PHP projects. I suggest we add a simple phpcs.xml for PHP CodeSniffer to check against PSR12 (as the CodeSniffer option is written). Then we have the following to follow up on:

• Codacy will pick up phpcs.xml (Add basic PHP CodeSniffer rule set #363) and phpmd.xml (PHP Mess Detector ruleset #265) config once you've selected them in the web interface.
• Codeclimate needs a config file to pick up a phpmd.xml and only seems to have the option to configure codeSniffer from the Codeclimate config. Add Code Climate config file for PHP checks #365
• GitHub Actions could be used to run either/both checkers, but then it would be good to merge Create GitHub Action scripts to replicate travis build testing #288 first.

[gregcorbett]

So after #365, codeSniffer on Codeclimate will check the code against PSR12?

[tofu-rocketry]

So after #365, codeSniffer on Codeclimate will check the code against PSR12?

Theoretically. It seemed impossible to tell while I was just working on a branch. Might be able to check now.

[tofu-rocketry]

Ok, Codeclimate knows that the config is coming from a .codeclimate.yml so I guess this is now done.