curl - Google Cloud Message API Notification Data doesn't appear - PHP

im sending notifications to my clients with PHP. Here is my PHP Code for this

<?php

define( 'API_ACCESS_KEY', 'AIzaSyAYq7KpB5J7x3p3zYyna...' );
$registrationId = array( $_GET['id'] );

$msg = array
(
    'message'   => 'here is a message. message',
    'title'     => 'This is a title. title',
    'subtitle'  => 'This is a subtitle. subtitle'
);
$fields = array
(
    'registration_ids'  => $registrationId,
    'notification'          => $msg
);

$headers = array
(
    'Authorization: key=' . API_ACCESS_KEY,
    'Content-Type: application/json'
);

$ch = curl_init();
curl_setopt( $ch,CURLOPT_URL, 'https://android.googleapis.com/gcm/send' );
curl_setopt( $ch,CURLOPT_POST, true );
curl_setopt( $ch,CURLOPT_HTTPHEADER, $headers );
curl_setopt( $ch,CURLOPT_RETURNTRANSFER, true );
curl_setopt( $ch,CURLOPT_SSL_VERIFYPEER, false );
curl_setopt( $ch,CURLOPT_POSTFIELDS, json_encode( $fields ) );
$result = curl_exec($ch );
curl_close( $ch );
echo $result;
Copy code

When i execute the script with my registration id there is notification like this, Notification

Title is Push message Body is The Message

As you can see, Notification title and message body is not equal with mines. How i can fix this ? Thank you.