In a new post Gonzalo Ayuso about a system he's developed to create real-time notifications for PHP applications using a mix of PHP and javascript (jQuery).

Real time communications are cool, isn't it? Something impossible to do five years ago now (or almost impossible) is already available. Nowadays we have two possible solutions. WebSockets and Comet. [...] I prefer to use comet (at least now). It's not as good as websockets but pretty straightforward ant it works (even on IE). Now I'm going to explain a little script that I've got to perform a comet communications, made with PHP.

His little sample application detects when a user has clicked on a link by subscribing to an event and using the javascript callback to send the message of a click event and wait for a response. You can find the complete code for the example over on github.