PHP 5 was kind of slow, to a point it threatened the future of Facebook (now Meta). They eventually went to transform it to CPP for speed improvement hiphop-cp

PHP 5 was kind of slow, to a point it threatened the future of Facebook (now Meta). They eventually went to transform it to CPP for speed improvement hiphop-cpp then went to build a VM with jit compilation. You could then deploy your app by transfering a sqlite file containing the compiled byte code. At Wikimedia we adopted it which has cut our CPU usage by half and has saved a few hundred of servers. We had some Facebook engineers helping which involved patching the Linux kernel while at it. Those were good times. Eventually PHP 7 followed up with a similar approach and had more or less the same performance as HHVM. Facebook went then to focus on the Hack language (a dialect of PHP with strong typing) and eventually phased out back compat with Zend. From what I remember, Sara Golemon at Facebook has done a lot of outreaching to Open Source project and gave us a lot of assistance (as well as others at Facebook).