Make AJAX call wait for event in php

Question

I do not know if my tile line is clear enough... My problem is: I have a JS application that needs to wait for an event on the server. At the moment it polls continuous the server data via XMLHttpRequest every second.

What I am thinking about is: Is it possible to make the call wait until for example a variable in PHP changes?

I hope that my question is clear enough.

Thanks!

Answer 1

You're looking for long polling (colloquially known as Comet). There are many examples on SO and elsewhere.

• http://blog.perplexedlabs.com/2009/05/04/php-jquery-ajax-javascript-long-polling/
• How do I implement basic "Long Polling"?
• http://www.contentwithstyle.co.uk/content/long-polling-example-with-nodejs
• http://www.zeitoun.net/articles/comet_and_php/start