I have a webpage with a Facebook Like button (social plugin). I need to show extra information on my page when the user has liked the page.
I know there has been similar questions but the answer has been to use the edge.create event to react to the user clicking the like button. This works fine except when the like happened prior to loading the page.
Others have suggested using a signed_request but I believe this is only applicable to canvas applications,
I know I can use the API to check for the like but this requires the user to grant permissions, but I want to do this in an anonymous manner (I am not interested in knowing who the user is, I just want to know if they liked the page).
Is there any way to do it?
Well this is exactly the difference between having a canvas app and a site that just uses the plugins. The plugin allows (you to allow) the user to like a certain URL and that's about all. In order for the site operating outside of Facebook at explicitly access that data, it'll need the correct permissions as you have noted... the user_likes permission.
Without a signed_request or the relevant permissions from the user, I do not believe that you'll be able to differentiate between users that have "liked" your URL.