Issue With Sending Data With PHP To GCM API

Question

i'm sending notification to who visited my website and accepted for sending desktop notifications to them. I'm taking theirs registration id and making request to gcm api.

BUT

I can not send Notificaiton title,message and icon.

Here is my PHP class taked from GCM with PHP (Google Cloud Messaging)

class GCMPushMessage {
    var $url = 'https://android.googleapis.com/gcm/send';
    var $serverApiKey = "";
    var $devices = array();

    /*
        Constructor
        @param $apiKeyIn the server API key
    */
    function GCMPushMessage($apiKeyIn){
        $this->serverApiKey = $apiKeyIn;
    }
    /*
        Set the devices to send to
        @param $deviceIds array of device tokens to send to
    */
    function setDevices($deviceIds){

        if(is_array($deviceIds)){
            $this->devices = $deviceIds;
        } else {
            $this->devices = array($deviceIds);
        }

    }
    /*
        Send the message to the device
        @param $message The message to send
        @param $data Array of data to accompany the message
    */
    function send($message, $data = false){

        if(!is_array($this->devices) || count($this->devices) == 0){
            $this->error("No devices set");
        }

        if(strlen($this->serverApiKey) < 8){
            $this->error("Server API Key not set");
        }

        $fields = array(
            'registration_ids'  => $this->devices,
            'notification'              => array( "message" => $message ),
        );

        if(is_array($data)){
            foreach ($data as $key => $value) {
                $fields['data'][$key] = $value;
            }
        }
        $headers = array( 
            'Authorization: key=' . $this->serverApiKey,
            'Content-Type: application/json'
        );
        // Open connection
        $ch = curl_init();

        // Set the url, number of POST vars, POST data
        curl_setopt( $ch, CURLOPT_URL, $this->url );

        curl_setopt( $ch, CURLOPT_POST, true );
        curl_setopt( $ch, CURLOPT_HTTPHEADER, $headers);
        curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );

        curl_setopt( $ch, CURLOPT_POSTFIELDS, json_encode( $fields ) );

        // Avoids problem with https certificate
        curl_setopt( $ch, CURLOPT_SSL_VERIFYHOST, false);
        curl_setopt( $ch, CURLOPT_SSL_VERIFYPEER, false);

        // Execute post
        $result = curl_exec($ch);

        // Close connection
        curl_close($ch);

        return $result;
    }

    function error($msg){
        echo "Android send notification failed with error:";
        echo "\t" . $msg;
        exit(1);
    }
}

Here is my notification.php file

$apiKey = "MY_API_KEY";
$devices = array('eBLwIaqdgOs:APA91bG-6Ry1gN1wg2jI3WOpgpQg2bxE1NxgJCBXxzE188GF46JuPO1DkWw-OiKswRr2y0K6xX8k4RKGOHqnub0zgoqgX22I1TDxOAWHrNoTn9XoRMWywARrWAq1zD78fAz3H9VcnqSW');
$message = "The message to send";
$gcpm = new GCMPushMessage($apiKey);
$gcpm->setDevices($devices);
$response = $gcpm->send($message, array('title' => 'Test title'));

echo $response;

And here is my sw.js file (service worker)

'use strict';
console.log('Started', self);

self.addEventListener('install', function(event) {
  self.skipWaiting();
  console.log('Installed', event);
});

self.addEventListener('activate', function(event) {
  console.log('Activated', event);
});

// TODO


function showNotification(title, body, icon, data) {
  console.log('showNotification');

  var notificationOptions = {
    body: body,
    icon: icon ? icon : '/images/touch/chrome-touch-icon-192x192.png',
    tag: 'simple-push-demo-notification',
    data: data
  };
  return self.registration.showNotification(title, notificationOptions);
}

self.addEventListener('push', function(event) {
  console.log('Received a push message', event);
  if (event.data) {
    console.log('message data', event.data);
    console.log('message data', event.data.text);
    var output = event.data.text();
    console.log(output);
  }
  showNotification("My Title","My Message");
});

When i requsted to my notification.php file a notification appears to me or which registration id i wrote with the title My Title and message My Message

As you can see thesee datas are coming from sw.js but i wont to send them via php because they are dynamic variables i'll get them from user input.

Help me with that please. Thank you.