Hidding user informations,

Im building web app which include user authentification, so every user will have profile with personal data. Data will be stored in db, but due to their privacy users can choose which of their informations will be displayed to public visitors. Let say someone want to hide his phone number from others, so he will go to account setings and choose "hide" option. But I cant figure out how to make it with db and rest of app. Any guidance or reference will be helpfull. Thanks