PHP fake sql run

Not sure if this should be located in php or javascript. Reason is that I am attempting to do some long polling; however, I am wondering if there is a way to increase the timeout to (pretty much unlimited) until there is a response from the client. Either using AJAX timeout property or some trick in php. I know in php if a sql is running in will 'extend' the timeout unless the ini timeout hits. Again I wonder if there is a way to fake a response like a sql running.

Thanks,
Deadweight