/*
Create a new library file called MY_Controller:
class Administrator extends Controller
*/
{    
    function Administrator()
    {
        parent::Controller();

        // Protect the admin area, etc
        $this->access->restrict('Administrators');
    }

}
/*
Then for your admin controllers you extend the Administrator class instead of the Controller.  That way you have common administrative logic in one place.
*/

http://codeigniter.com/forums/viewthread/82397/#414367

CI extend library

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