Push notifications from server to user with PHP/JavaScript

Question

Short: Is there a way to push data from the server to a logged in user session without that user needing to make an HTTP request?

Long(er):<

Answer 1

I recommend Socket.io

It leverages

WebSocket, FlashSocket, HTML file(for IE), XHR long-polling, JSONP-polling

It is with Node.js which means it is on non-blocking nature.

In realtime feature, concurrency is a big issue

so the non-blocking nature of Node.js and Socket.io would help you