elgg_ok_response($content= '', string|array $message= '', string $forward_url=null, int $status_code=ELGG_HTTP_OK)
Prepares a successful response to be returned by a page or an action handler.
elgg_error_response(string|array $message= '', string $forward_url=REFERRER, int $status_code=ELGG_HTTP_BAD_REQUEST)
Prepare an error response to be returned by a page or an action handler.
notify_user(int|array $to, int $from=0, string $subject= '', string $message= '', array $params=[], $methods_override=null)
Notify a user via their preferences.