GrumPHP is a code-quality tool written in PHP that executes code-quality checks pre-commit.
Having tests and code quality checks running in your Continuous Integration setup is great but in an ideal world, you don't want to have bad code committed in the first place. This shortens the feedback cycle which is always good.
We are using GrumPHP in some of our projects to get a feeling which checks should be run and if/how much it improves our work. If GrumPHP shows to be helpful and we set on a range of standard checks, we might adopt it and roll it out across our projects.