title: Facebook API - how to get page ID using Facebook API?
body: <p>With Facebook API, within a custom app added to a fanpage (tab app), how do I get the fanpage ID?</p>
  
  <p>Here's what I'm trying to achieve:</p>
  
  <ul>
  <li>user goes to the full-width canvas app, he authorizes himself there and allows the app to add a tab to one of the fanpages he's administrating</li>
  <li>every Facebook user going to that fanpage, sees the tab and the tab shows content specific to that fanpage (that's why I need to know the fanpage ID)</li>
  <li>if fanpage administrator wants to change something, he goes to the full-width canvas and logs in to my service (here's where I store what he wants to show in his Fanpage)</li>
  </ul>