a quite simple chat that saves all messages into mysql (see mysql.sql in zip), it remembers users nicks and allows users to change them too, auto updates messagebox, shows online & offline users, requires javascript (jquery, libraries included in zip), mysql, php, need to make it more secure and maybe in next version connect it to a irc server
Demo: http://nx.cf.gs/chat/
As far i analyzed its not a relay chat. Every message is stored into MySQL Database. So when you connect to the room you can see all messages has been sent to the room, My guess or you can see whatever is posted after your join... Its basically simple and neat. Haven't tested but from the code even its messy seems fine.
http://nx.cf.gs/chat/