[frik]

The development cycle with PHP/Hack is fast. You code, then press F5 in the browser and see result instantaneous. With other languages, a static compilation time of even just a few seconds is very contra productive and annoying. Writing less (redundant) code helps a lot with prototyping too (dynamic typing, optional static types). The documentation on php.net with comments on each page (from the community) is very good.

Node/IO.js and Go have their advantages, especially if one wants to use WebSocket.

Nowadays, half of the code is client side anyway (be it HTML5 JS (maybe with React/Angular) or mobile apps) - in such cases the server output and receives a lot of JSON. And then Node.js/Go/HHVM are about equal as good in benchmarks, at least in my personal benchmarks (10.000 -100.000 requests/s with Apache AB tool).