Fxmlrpc\MulticallBuilder::invokeHandler PHP Method

    protected function invokeHandler($onSuccess, $onError, $isError, $result)
    {
        if ($isError && $onError !== null) {
            call_user_func($onError, $result);
        } elseif ($onSuccess !== null) {
            call_user_func($onSuccess, $result);
        }
    }