// Users_Controller

    public function ajax_update()
    {
        if ($input = $this->input->post()) {

            $user = new User_Model(Session::get('user_id', FALSE));
            $profile = new Profile_Model(Session::get('user_id', FALSE));

      // I get an error because I try to pass $input to a second model (expecting an array) but it is now and object
      // would the best way to be use $input_user and $input_validate then merge error arrays?
            if ($user->validate($input, 'update') && $profile->validate($input)) {

                if ( ! empty($input['password']))
                    $user->hashed_password = Auth::hash_password($input['password']);

                $user->save();
                $profile->save();

                $json = array('success' => TRUE);
                $this->template->body = json_encode($json);

            } else {

                foreach ($input->errors('form_errors') as $error) {
                    $errors[] = $error;
                }

                $json = array('success' => FALSE, 'errors' => $errors);
                $this->template->body = json_encode($json);
            }
        }
    }

////////////////////////
//////////////////////
///// User_Model extends ORM
///// has_one profile

    public function validate(array & $input, $action)
    {
        $input = new Validation($input);

        if ($action == 'update')
            $input->pre_filter('trim')
                     ->add_rules('name', 'required')
                     ->add_rules('email', 'required', 'valid::email')
                     ->add_rules('email', array($this, '_unique_email'))
                     ->add_rules('password', 'length[4,20]')
                     ->add_rules('password', 'matches[confirm_password]');

		return parent::validate($input);
    }

////////////////////////
//////////////////////
/////
class Profile_Model extends ORM {
    protected $belongs_to = array('user');
    protected $primary_key = 'user_id';

	public function validate(array & $validate)
	{
        $validate = new Validation($validate);

        $validate->pre_filter('trim')
                 ->add_rules('phone_number', 'phone[10]')
                 ->add_rules('major', 'standard_text')
                 ->add_rules('website_url', 'url')
                 ->add_rules('linkedin_url', 'url')
                 ->add_rules('image_url', 'url')
                 ->add_rules('bio', 'standard_text');

		return parent::validate($validate);
	}
}