Who doesn't know stof? He is an active contributor to so many PHP Open-Source projects that I just can list them all here. He is one of the top 10 Symfony contributors and his first contribution dates as far back as 2010 when he fixed a typo!
Besides contributing code, he is also one of the most active community members when it comes to helping people; he won the Best Support on Mailing-List award in 2011 and the Best Community Support in 2013.
As of now, he has the power to merge pull requests for the following Symfony components and bridges: - BrowserKit,Config, Console, DependencyInjection, DomCrawler, EventDispatcher, HttpFoundation, HttpKernel, Serializer, Stopwatch, DoctrineBridge, MonologBridge, and TwigBridge.