IMHO, the biggest reason to use a language like Node when you want to do async programming is that for any random library you choose there's a 98% chance that it properly supports async as well and won't block on you. For better or worse async is pervasive in the ecosystem. Even in good languages like Python that have (allegedly; I've not used them) good async frameworks, most libraries will block as it's the normal I/O mode for the language, which really limits what you can use. I can't imagine the situation will be any better in PHP.
Or, even better, you could just use a language that works well with concurrent programming without having to shoehorn in abstractions that break 2% of the time. Go, Haskell, Erlang, take your pick; any of them will work correctly out of the box, even if some library does blocking FFI calls.
People keep saying that Node is async native, but the GC is global and synchronous, and that property will bite you on availability even at moderate traffic, i.e. sooner than you'd expect.
