It was initially implemented with websockets but that meant having to actually run a websocket server alongside the PHP app to work. Caleb went the simple route

It was initially implemented with websockets but that meant having to actually run a websocket server alongside the PHP app to work. Caleb went the simple route by just sticking to AJAX instead. It's a difference in how PHP is typically run (mod_php or fastcgi) vs how Erlang runs (standalone server). On his blog, he posted some videos earlier this year about the process of coming up with what eventually became Livewire, as well as a bunch of discussion on his podcast No Plans To Merge.