Today, Facebook has published a new article in the developer blog discussing how to handle revoked auth permissions in Facebook apps, http://developers.facebook.com/blog/post/576/.
The article is good in the sense that it has explained the concept. However, developer may have problem in running the example. If you have taken a look at the comments provided by other developers, there are already people complaining that the example is bad as most browsers will block the popup (as it is initiated not from a user action).
Don’t blame the author please. I believe he tries to help and share the idea with other developer. “Example” or “sample code” is always “just an example/sample”, it may not be perfect as it just aims to show or illustrate the main idea and give you a sample way for doing it. Before taking the sample code and use it in your own app, do review the code and test it.
For me, I prefer to do the checking at the server end. If needed, I simply solve the issue (i.e. to request for the revoked permission again) by initiating the OAuth 2.0 authentication flow. This is pretty standard and easy by using the PHP SDK.