Which fcm registration id has failed when targeted for multiple registration_ids

Question

I'm sending notifications to several registration ids from server side in php. This is the request:

public function androidPushNotification($registration_ids, $title, $message) {
    $msg = array (
            'message' => $message,
            'title' => $title 
    );

    $fields = array (
            'registration_ids' => $registration_ids,
            'data' => $msg 
    );
    
    $headers = array (
            'Authorization: key=' . $this->API_ACCESS_KEY,
            'Content-Type: application/json' 
    );
    
    $ch = curl_init ();
    curl_setopt ( $ch, CURLOPT_URL, $this->GCM_URL );
    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 );
    
    return $result;
}

The registration_ids variable has two registration ids in an array, one of them is from an old installation of the client app and the other is the current one.

I'm getting this response from fcm:

{
  "multicast_id": 7860323906688398625,
  "success": 1,
  "failure": 1,
  "canonical_ids": 0,
  "results": [
    {
      "error": "NotRegistered"
    },
    {
      "message_id": "0:1478735313889582%1b153de0f9fd7ecd"
    }
  ]
}

How can I know which of the registration ids has failed?

Is there another option to get this info?

Answer 1

I have found the answer:

The result array is in the same order that the registration ids. For example, if the request is:

$fields = array (
            'registration_ids' => array('123456','987654'),
            'data' => array ('message' => 'This is the message','title' => 'Hi there!')
);

The example response:

{
  "multicast_id": 7860323906688398625,
  "success": 1,
  "failure": 1,
  "canonical_ids": 0,
  "results": [
    {
      "error": "NotRegistered"
    },
    {
      "message_id": "0:1478735313889582%1b153de0f9fd7ecd"
    }
  ]
}

The registration id has failed is the 123456 one.

From the gcm documentation:

Here are JSON results for 6 recipients (IDs 4, 8, 15, 16, 23, and 42 respectively) with 3 messages successfully processed, 1 canonical registration token returned, and 3 errors:

{ 
  "multicast_id": 216,
  "success": 3,
  "failure": 3,
  "canonical_ids": 1,
  "results": [
    { "message_id": "1:0408" },
    { "error": "Unavailable" },
    { "error": "InvalidRegistration" },
    { "message_id": "1:1516" },
    { "message_id": "1:2342", "registration_id": "32" },
    { "error": "NotRegistered"}
  ]
}

In this example:

• First message: success, not required.
• Second message: should be resent (to registration token 8).
• Third message: had an unrecoverable error (maybe the value got corrupted in the database).
• Fourth message: success, nothing required.
• Fifth message: success, but the registration token should be updated in the server database (from 23 to 32).
• Sixth message: registration token (42) should be removed from the server database because the application was uninstalled from the
  device.

I hope it helps, regards.