“error”:”InvalidRegistration” while sending notification from PHP

Trying the mentioned code with registeration_ids and to parameter and both are not working. Help me to solve the same. Every time it is giving this error of multi cast id and InvalidRegistration. Getting this error: {"multicast_id":8367359766XXXXXXXXX,"success":0,"failure":1,"canonical_ids":0,"results":[{"error":"InvalidRegistration"}]}

function send_notification () {
    $fcmUrl = 'https://fcm.googleapis.com/fcm/send';
    $args = func_get_args();
    $response = ["status" => 0, "message" => "Notification couldn't be sent"];

    $title = "Hey test notification";
    $body = "";
    $apiKey = "QWERTYHHVCFVBVBN";//Server key under the Project settings
    $tokenArr = ["XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX","YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY"];
    $refId = 123;
    $msgNotification = [
        "title" => $title,
        "body" => $body
    ];
    $extraNotificationData = [
        "refId" => $refId,
        "title" => $title
    ];

    $fcmNotification = [
        "registration_ids" => $tokenArr,
        "notification" => $msgNotification,
        "data" => $extraNotificationData
    ];
    $headers = [
        "Authorization: key=" . $apiKey,
        "Content-Type: application/json"
    ];
    
    $encodedData = json_encode($fcmNotification);
    // echo "<pre>";print_r($fcmNotification);exit;
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL,$fcmUrl);
    curl_setopt($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, $encodedData);
    $result = curl_exec($ch);
    if ($result === FALSE) {
        die("Curl failed: " . curl_error($ch));
    }
    print_r($result);exit;
    curl_close($ch);
    $response = ["status" => 1, "message" => "Notification sent to users", "payload" => $result];

    return $response;
}

Answer

Invalid Registrations usually have one of the following reasons:

• The registration token/device token is invalid
• The client app has actively unregistered with FCM
• The client app has been automatically unregistered with FCM because the app has been uninstalled.
• The device token has expired – this can happen when Google refreshes device tokens, or, in case of iOS devices, when the APNs token has expired
• The API key belongs to a different Firebase project than the device you’re sending the message to. A common reason for this is when you’re using multiple environments and, for example, a token has been registered with the prod environment, but you’re trying to send a message from a staging environment.

In all cases, except the last one, you can remove the registration token from your server and stop sending notifications to it.

The $fcmUrl = 'https://fcm.googleapis.com/fcm/send'; shows that you’re using the legacy FCM API to send your messages. Please note that, unless you’re relying on device group notifications, Google recommends migrating to the newer HTTP v1 API.