All code is Symfony2 Code formatted, so every pull request must validate phpcs standards. You should read Symfony2 coding standards and install this CodeSniffer to check all code is validated.
There is also a policy for contributing to this project. All pull request must be all explained step by step, to make us more understandable and easier to merge pull request. All new features must be tested with PHPUnit.
If you'd like to contribute, please read the Contributing Code part of the documentation. If you're submitting a pull request, please follow the guidelines in the Submitting a Patch section and use the Pull Request Template.