title: how to handle log in through Facebook?
body: <p>I am developing a webapp with PHP as backend, and I wanted the user to be able to login through a few social media(fb, linkedin, insta).
  I had gone through Facebook's login API and am still confused.</p>
  
  <p>Here are the bit I needed through the login:
  1. Bio Details
  2. User's link to social media</p>
  
  <p>To get these information I will need to ask for permission and I can get both of the information I needed.</p>
  
  <p>But here is what I don't understand</p>
  
  <p>Questions:
  1. Other than the 2 information needed, what else should I store in the database? (Accesstoken?)
  2. How can we authenticate the user? through which information returned from the API?(Accesstoken, id or ?)</p>