I see many sites on the net that offer free public self profile pages to their visitors. They also offer the option to make the profile pages private through the use of a checkbox in a form. How can they program this through their db? Is there a php code you can write on a web page that makes it password protected - then the username and password must match what's in the db?
It's just a bit that needs to be switched on and off. If each time that page loads (outside of cache) you check to see if some check bit is turned on, then you validate the user, otherwise you let them through.
Could be many different ways to implement this, but what works best for you only you would know.