从控制器中的 ajax 调用中检索数据

我有一个 ajax 调用，它正在向我的一个控制器发送一些 ID。

运行此操作的jQuery基本上是搜索具有像notification-id-这样的ID的元素，然后获取ID并将它们存储在JavaScript变量中。

当我alert()或console.log()这个变量时，它会打印出我在页面上的两个通知的1,2值 notification-id-1 和 notification-id-2.

对于我的 ajax 调用，我只是在下面做：

$.ajax({
  url: "{{ url('/notifications/read') }}",
  method: "POST",
  data: notifications, // Let jQuery handle packing the data for you
  success: function(response) {
       // The data was sent successfully and the server has responded (may have failed server side)
   alert(notifications);
  },
  error: function(xhr, textStatus, errorThrown) {
      // AJAX (sending data) failed
  },
  complete: function() {
      // Runs at the end (after success or error) and always runs
  }
});

我正在尝试通过执行dd($request->all());来测试我的控制器正在接收的内容，但这只是返回：

array:1 [
  "undefined" => ""
]

（ajax 调用成功运行）

如何在控制器中检索在此 ajax 调用中发送的 ID 值？

编辑：完整脚本

<script type="text/javascript">
  $(document).ready(function() {
    var count = $('#notification-counter');
    var new_notifications = $('#notification-new-counter');
    $('#notification-drop-down').on('click', function() {
      count.empty();
      var notifications = $('[id^="notification-id-"]').map(function() {
        return this.id.slice(16);
      }).get();
        $.ajax({
          url: "{{ url('/notifications/read') }}",
          method: "POST",
          data: notifications, // Let jQuery handle packing the data for you
          success: function(response) {
               // The data was sent successfully and the server has responded (may have failed server side)
               alert(notifications);
          },
          error: function(xhr, textStatus, errorThrown) {
              // AJAX (sending data) failed
          },
          complete: function() {
              // Runs at the end (after success or error) and always runs
          }
        });
    });
  });
</script>