尝试发送通知时出现致命错误-Web Push PHP Lib

Question

我正在尝试使用PHP Web推送库发送推送通知。一切工作正常，但突然在发送通知时出现致命错误。

这是我用来发送通知的代码：

<?php
require "/vendor/autoload.php";

use Minishlink\WebPush\WebPush;
use Minishlink\WebPush\Subscription;

$auth = array(
    'VAPID' => array(
        'subject' => 'https://www.example.com/',
        'publicKey' => 'public key is here',
        'privateKey' => 'private key is here',
    ),
);

    $con = mysqli_connect("localhost","user","pass","db");

    // Check connection
    if (mysqli_connect_errno())
      {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
      }else{
          echo "connected";
      }
      $selectsql = "SELECT * FROM subscription";
      $rowcount = mysqli_num_rows(mysqli_query($con,$selectsql));
      $result = $con->query($selectsql);

            if ($result->num_rows > 0) {
                while($row = $result->fetch_assoc()) {

                     $endpoint = $row["endpoint"];
                     $publickkey = $row["publick_key"];
                     $userauthtoken = $row["user_auth_token"];


                    $title = 'Title is Here';
                    $body = 'Content is Here';
                    $icon = 'https://www.example.com/fav.png';
                    $image = 'https://www.example.com/feature-image.jpg';
                    $link = 'https://www.example.com/landing';
                    $jsonarray = '["'.$title.'", "'.$body.'", "'.$icon.'", "'.$image.'", "'.$link.'"]';

                    $webPush = new WebPush($auth);

                    $res = $webPush->sendNotification(  
                            $endpoint,
                            $publickkey,
                            $userauthtoken,
                            $jsonarray,
                            true  // I'm getting an error here on line 55
                        );
                }
            }
?>

这是我在日志中遇到的错误：

2018/12/02 16:43:22 [error] 3627#0: *55 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Uncaught TypeError: Argument 1 passed to Minishlink\WebPush\WebPush::sendNotification() must be an instance of Minishlink\WebPush\Subscription, string given, called in /webpush/send.php on line 55 and defined in /vendor/minishlink/web-push/src/WebPush.php:108

服务器：Nginx-CentOS 7 数据库服务器：MySQL 5.6 PHP：v7.2

我尽力在Web和stackoverflow上找到解决方案，但我认为我在找错地方。请在这里指导我！