I've been coding PHP, Java and more recently JS for a while. I feel like PHP has dropped the ball when it comes to async programming compared to the others. I think that's one of the reasons why facebook forked PHP (hacklang.org) to make it async friendly. ReactPHP is slow compared to node, and the fastest PHP async framework, Swoole by Tencent, is still limited in what it supports. I've been trying vert.x on Java which isn't bad and not minding koa. I feel like they need to do more to support projects like ReactPHP with native extensions like Swoole.