im using comet to push new data to the user.1: but i wonder how i should check if new data (new messages, new replies etc) is available?should i in the php in the background use a while loop and sleep it for 1 min so it can check every one min if new data has come in?or should i have a trigger in the database for this?what available options are there?2: and how can i actually check eg. if user got a new message with SQL? how should i set up "the system"?