Code logic in codeigniter

so you would start out like you are doing and your get_user_details($user_id) method is in your controller.
but then as you refactor, basically that entire method could be refactored into a model, so then the controller
is just asking the model for $user and then passing $user to appropriate view.

the idea is that as you change specific details about the user link, or the profile picture, etc -
all of that detail is in a model method. the advantage is that your controller does not need to change at all.
AND if any other controllers need $user, you get it from the same model, instead of having to repeat the $user code in another controller.
AND again any changes to the $user method in the model - the other controllers are always getting the latest version.