I am looking to create a Web Chat system using PHP, MySQL and JavaScript.
Currently, I am storing messages in a MySQL database with an incremental ID (Yes, it is indexed), a timestamp, the sender, and the message itself. I am then using AJAX to query the database every 500ms, seeing if there are any more recent messages than the last one received. However, I have a feeling that this is probably horribly inefficient as it will result in a large load on the MySQL server when multiple users are online. Having looked around a bit on Google and on here, everything seems to point to this way of doing it.
My question: is there a better way to do this? Any tips on how to reduce the load on the server would also be welcome.
I’m using PHP 5.3, on an Apache webserver, so libraries or plugins compatible with those would be fine.
EDIT:
Forgot to mention in the original post, but I’m not worried about supporting IE or other outdated browsers.
You should look into ajax long polling, in a nutshell this a simple ajax call but will not return a result from the server if there is no new data. You just do a simple loop on the server side until new data will be available then return it. Of course you have to stop this eventually if there’s no result to send to client after a while (eg. 1 minute) then restart the call.