Accessing LogedIn user Id in facebook Page?

Here I am Using Signed Request in facebook :

http://developers.facebook.com/docs/authentication/signed_request/

Here As per document in json object contain following field :

"user", "algorithm", "issued_at", "user_id", 开发者_JAVA百科"oauth_token", "expires", "app_data", "page", profile_id

In my code here I am getting json object successfully but I missed "user_id" their is something I have missed here ?????

Thanks for suggestion..

On the Facebook documentation page you linked to, it says:

"If the user has not authorized your application, your application will only be passed a subset of the above information."