The point is that by using the same language for all things in the web app, code can be shared. For example, the class for session handling (I keep session info in a database), database connection, etc. so that future maintenance of the web application does not require changes to the php side of things and then the Javascript port of the php side of things. You can update a single class that both the main web app and the server side EventSource page.
Of course the web developer needs to know Javascript for the client side programming, but the client side programming doesn't interface with server resources directly, it sends those as requests to the web application.
If I have to do that part of the web app in node.js I'll do it in node.js but I would prefer to do it in php because the rest of the web app (a social network platform) is php. What I'm trying to do is leverage the power of html5 to remove all use of plugins. I hate browser plugins with a passion. Probably from my days running ppc linux where there were none so any site that required them was broken, but hell, I even hate dependence upon them in Windows. To keep everything server side php is why I'm seeking a php capable http server that does not have the same persistent connection limitations of Apache.