like page request in tab application

Facebook removed the ability to 'gate' a Facebook Page based on if a user Likes it. The new policy was announced, and immediately took effect, on August 7th.

For more information, see their Facebook Graph API v2.1 announcement post. Specifically:

The liked field will no longer be returned in the page property of the signed_request object for Page Tab apps created from today onwards. For apps created before today, from November 5, 2014 (90 days from today), the liked property will always return true regardless of whether or not the person has liked the page.

I hope that helps answer your question,
Alex

There's no way to detect if the user is a fan or not. That ability has been removed by Facebook. There are many lightbox solutions on there that can always popup on the page when the user visits. There will be no way to only pop a lightbox up if the user hasn't Like'd the Page though.

I hope that helps answer your question,
Alex