Hello i have only just started learning Php but i will try and help,

Firstly i would create a Php page were members would be notified that they need to update there account,

Then i would create a mysql database using Unique ID to hold the members updated account information,

I would then link the mysql database to your Php page,

lastly create a form that the members fill in to update there member information, this information should go directly into your mysql databse mentioned above,

You could then use the php echo fuction to drag the logged in users information from the databse and display who's online or not. Its not as hard as it seems.

If you need help creating the database to get you started let me now.

hope this helps