I have installed SublimeLinter and SublimeLinter-phpcs. Setting debug:true gives the full phpcs output in the console (so phpcs is called correctly), but the left bar in the project view does not mark the issues.
To check, I also installed SublimeLinter-php. That works just fine: syntax errors are marked in the project view.
This issue is copied from SublimeLinter/SublimeLinter#1988
I propose adding instructions to the README.