I am not good in PHP, AJAX, jQuery and JS. I am exploring and doing self study on a chat application on web. But I can't figure out why every time the message received by the other user, it duplicates as if its copying all the recent messages plus the new message. This is the link of the file - https://www.dropbox.com/s/5v74vygr3jti2lo/mychat_05022013t.zip so you can test it for yourself. Hope I am clear.
Thanks in advance for all your help.