获取未注册令牌

Question

我的代码是：

    include('db.php');
$sql = $pdo->prepare('SELECT * FROM token');
$sql->execute();
$data = $sql->fetchAll();
foreach($data as $row) {
    $tokens[] = $row['token'];
}
define('SERVER_API_KEY','AIzaSyBjFxBF35xzO9CkqzF4_56_VRxYkF41lL0');
$msg = [
    'title'=>'Testing',
    'body'=>'Testing',
    'icon'=>'icon.png',
    'image'=>'image.png'
    ];
$header = [
    'Authorization: Key=' . SERVER_API_KEY,
    'Content-Type: Application/json'
    ];
$payload = [
    'registration_ids'=> $tokens,
    'data'            => $msg
    ];
    $curl = curl_init();
    curl_setopt_array($curl, array(
        CURLOPT_URL => "https://fcm.googleapis.com/fcm/send",
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_CUSTOMREQUEST => "POST",
        CURLOPT_POSTFIELDS => json_encode($payload),
        CURLOPT_HTTPHEADER => $header
        ));

    $response = curl_exec($curl);
    $err = curl_error($curl);
    curl_close($curl);

    if ($err) 
    {
        echo 'cURL error #:'.$err;
    } else echo $response;

我想知道如何获取无法通知的令牌并给我错误：“ error”：“ NotRegistered”？是否可以从我的数据库中删除所有未注册的令牌？