Hi guys

I have developed a chat application using PHP and jQuery. So, at the moment, my chat app would poll the server every 2.5 seconds, with the last message's id as GET request. And in the server side, the script will establish a db connection and check whether any new messages are arrived which is greater than the message_id that was received through GET request.
If found, echo the new messages. Otherwise, echo empty string. So far it works okay.

But I have heard that we could make the polling efficient by using a long polling method or a comet programming method. Based on the my research(search done on Google ), I found that comet is not cross-browser supporting. So, I thought about the long polling mechanism. But what it does is, it would use a loop in the serverside, checking for new data arrivals and if so, echo it. Otherwise, stay in the loop until new messages comes.
But wouldn't it eat server resource ?

Do you think long polling would be the best ? Or do you know some other technique which is more efficient ?

Thanks