How to show a pop up box if there is some result for the mysql query?

I have a message box in my project if one have to check some message they have to enter the message link to check message instead ,I am thinking of showing a message in a popup box if the query where i am fetching the messages is not empty ,,(i,e) if there is any unread message in users account must,trigger a popupbox with message ,,,,There is a new message in your message box,,, Does this process need开发者_JAVA百科s backround threading , should we work with some othertechnology to be integrated with php to complete the process?

of the top of my head, albeit there is surely some norm/best practice for this, use a js loop that runs every 30 secs that fires an ajax request that queries the database. If there are some results, update the appropriate fields.