SelectQuery::fetchColumn PHP Method

    public function fetchColumn($columnNumber = 0)
    {
        if (($s = $this->execute()) !== false) {
            return $s->fetchColumn($columnNumber);
        }
        return $s;
    }

 public static function remember($user)
 {
     //We need a user, but we won't remember the admin user.
     //if ($user && $user->id > 0 && !in_array('superadmin', $user->roles)) {
     if ($user && $user->id > 0) {
         $random = get_random('number');
         $persist = new PersistUserObj();
         $data = array('user_id' => $user->id, 'random' => $random);
         if ($persist->create($data)) {
             $query = new SelectQuery('PersistUser');
             $query->field('MD5(CONCAT(`id`, `user_id`, `random`))')->filter('`id`= :id');
             $hash = $query->fetchColumn(array(':id' => $persist->array['id']));
             if (setcookie('remembered', $hash, time() + 60 * 60 * 24 * 14, WEB_SUB_FOLDER)) {
                 return true;
             } else {
                 Backend::addError('Could not set cookie to remember login');
                 $query = new DeleteQuery('PersistUser');
                 $query->filter('`id` = :id')->limit(1);
                 $query->execute(array(':id' => $persist->array['id']));
             }
         } else {
             Backend::addError('Could not remember login');
         }
     } else {
         Backend::addError('Invalid user to remember');
     }
     return false;
 }