user login using FB for facebook app development

All you need to do is to replace the Uppercase Variables with your own real parameter. If the user dose not log into facebook, then it will redirect the user to the facebook login page; if the user user has loged into facebook but not authened your required permission, then it will prompt the user permission pannel. if the uer has loged into facebook and authened all your permission, it would direcly redirect the user into your app;