I am developing a social web application in php/mysql, I would like to hear your advice about what would be a better way to implement security. I am planning something like this:- At the presentation level, I restricting the user to see only those items/content he is eligible to see with the rights he is eligible & at the database level, whenever my data is read/ written or updated I verify that the person has rights to such interactions with that part of data. So for each action there is 2 layers of security one at the view level & another at the database level. Would double checking be much overhead ?

ofcourse this handles only with the internal security issues ..