public function setConfig($notificationData, $payloadData = [], $silentNotification = false, $scheduledDateTime = '', $sound = 'default')
    {
        if (!is_array($notificationData)) {
            $notificationData = [$notificationData];
        }
        if (count($notificationData) > 0) {
            $this->requestData = array_merge($this->requestData, ['notification' => $notificationData]);
        }

        // payload
        if (!is_array($payloadData)) {
            $payloadData = [$payloadData];
        }
        if (count($payloadData) > 0) {
            $this->requestData['notification']['payload'] = $payloadData;
        }

        // silent
        if ($silentNotification) {
            $this->requestData['notification']['android']['content_available'] = 1;
            $this->requestData['notification']['ios']['content_available'] = 1;
        } else {
            unset($this->requestData['notification']['android']['content_available']);
            unset($this->requestData['notification']['ios']['content_available']);
        }

        // scheduled
        if ($this->isDatetime($scheduledDateTime)) {
            // Convert dateTime to RFC3339
            $this->requestData['scheduled'] = date("c", strtotime($scheduledDateTime));
        }

        // sound
        $this->requestData['notification']['android']['sound'] = $sound;
        $this->requestData['notification']['ios']['sound'] = $sound;
    }