private function check_username($id, $args)
 {
     $str = $_POST[$id];
     $Users = new PerchUsers();
     // check for a passed in UserID
     // so that a user can be excluded from the check
     // (so we don't prevent editing of a record)
     if (isset($args['userID'])) {
         $exclude_userID = $args['userID'];
     } else {
         $exclude_userID = false;
     }
     if (!$Users->username_available($str, $exclude_userID)) {
         return false;
     }
     return true;
 }