PHP runtime have been controversial for years; because hosting is very important due to dynamic and modularity of PHP. So, what’s about opcode cacher? atomic deployment? file system usage? session management? code/data split? PHP VM or built in http server? Or maybe HHVM? So many question we have to answer building php support at Clever Cloud (managing A LOT of php apps on hosting PaaS), and many war stories to share about our choices.