It is known by now that every codebase large enough (in terms of lines of code or people collaborating to it) should follow any code standard. Here at Coolblue we weren’t different and were using our own coding standard. But codebases evolve. And our codebase – that has been supporting one of the most visited ecommerces in The Netherlands – needed to be upgraded to a coding standard that’s a little bit more up to date. This is the process we follow to move into PSR-2.

http://devblog.coolblue.nl/tech/converting-big-php-codebases-to-psr2/

In the past months we converted several of our old projects to PSR-2 with Fabien Potencier's coding standards fixer and had zero issues doing so. Hurray for standardized code.