Implementing the Callback

To parse and respond to the request, you should implement a “data deletion request” callback. Your callback must use the secure HTTPS protocol and must be listed in the Data Deletion Request URL field of your app’s Facebook Login > Settings page in the App Dashboard.

The Data Deletion Request callback that you implement must do the following:

• Initiate the deletion of any data your app has from Facebook about the user.
• Return a JSON response that contains a URL where the user can check the status of their deletion request and an alphanumeric confirmation code. The JSON response has the following form:
  { url: '<url>', confirmation_code: '<code>' }

Failure to comply with these requirements may result in your callback being removed or your app being disabled.

You can implement this callback in any language, but the following code is an example of the callback in PHP.

<?php
header('Content-Type: application/json');

$signed_request = $_POST['signed_request'];
$data = parse_signed_request($signed_request);
$user_id = $data['user_id'];

// Start data deletion

$status_url = 'https://www.<your_website>.com/deletion?id=abc123'; // URL to track the deletion
$confirmation_code = 'abc123'; // unique code for the deletion request

$data = array(
  'url' => $status_url,
  'confirmation_code' => $confirmation_code
);
echo json_encode($data);

function parse_signed_request($signed_request) {
  list($encoded_sig, $payload) = explode('.', $signed_request, 2);

  $secret = "appsecret"; // Use your app secret here

  // decode the data
  $sig = base64_url_decode($encoded_sig);
  $data = json_decode(base64_url_decode($payload), true);

  // confirm the signature
  $expected_sig = hash_hmac('sha256', $payload, $secret, $raw = true);
  if ($sig !== $expected_sig) {
    error_log('Bad Signed JSON signature!');
    return null;
  }

  return $data;
}

function base64_url_decode($input) {
  return base64_decode(strtr($input, '-_', '+/'));
}
?>

This produces a JSON object that looks like this, in which user_id is the relevant field for your callback.

{
   "algorithm": "HMAC-SHA256",
   "expires": 1291840400,
   "issued_at": 1291836800,
   "user_id": "218471"
}

For more information on signed requests, see Using a Signed Request in the Login for Games on Facebook topic.

Testing Your Callback

To test your callback:

1. Log in to your app with Facebook Login.
2. Go to your Facebook profile’s Apps and Websites settings tab: https://www.facebook.com/settings?tab=applications
3. Remove your app.
4. Click the View Removed Apps and Websites link.
5. In the popup, click the View button to the right of the application.
6. In the window, appeared click Send Request to trigger your callback.