php中的foreach循环验证失败

Question

这是我们的电子邮件通知中的代码。当用户更新个人资料管理员获取更新的特定字段的通知时。在表单中有更多100个字段。

我做了两个阵列。

//updated array
$compare_array=array_diff_assoc($updated_meta_data,$previous_data);
//previous array
$pre_data=array_intersect_key($previous_data,$compare_array);
if(!empty($pre_data) || !empty($compare_array))    {
foreach ($compare_array as $key => $value) {
if(empty($value) && empty($pre_data[$key]))
continue;
    $emailtext.="<tr>
    <td style='border:2px; border-style: solid;  border-collapse:collapse;'>$key</td>
    <td style='border:2px; border-style: solid;  border-collapse:collapse;'>{$pre_data[$key]}</td>
    <td style='border:2px; border-style: solid;  border-collapse:collapse;'>$value</td>

     </tr>";
}
}

我的调试结果在

之下

 ["fourth_guest_salutation"]=>
  string(2) "Mr"
  ["fourth_guest_first_name"]=>
  string(0) ""
  ["fourth_guest_last_name"]=>
  string(0) ""
  ["fourth_guest_email"]=>
  string(0) ""
  ["fourth_guest_country_code"]=>
  string(10) "+91- India"
  ["fourth_guest_contact_number"]=>
  string(0) ""
  ["fourth_guest_nationality"]=>
  string(5) "India"
  ["fourth_guest_id_doc"]=>
  string(0) ""
  ["fourth_guest_passport_picture_front"]=>
  string(0) ""
  ["fourth_guest_passport_picture_back"]=>
  string(0) ""
  ["fourth_guest_indian_visa"]=>
  string(0) ""
  ["fourth_guest_has_travel_details_as_first_guest"]=>
  string(2) "on"
  ["fourth_guest_visa_assistance"]=>
  string(2) "on"
  ["fourth_guest_arrival_date"]=>
  string(0) ""
  ["fourth_guest_name_of_airline"]=>
  string(0) ""
  ["fourth_guest_flight_number"]=>
  string(0) ""
  ["fourth_guest_city_of_departure"]=>
  string(0) ""
  ["fourth_guest_arrival_time_of_flight"]=>
  string(5) "00:00"
["fourth_guest_conn_arrival_time_flight"]=>
  string(5) "00:00"
  ["fourth_guest_has_conn_flight"]=>
  string(2) "on"
  ["fourth_guest_conn_city_of_departure"]=>
  string(0) ""
  table stricture are



column |previous data|updated data 
below is my email result.

fourth_guest_arrival_time_of_flight， fourth_guest_conn_arrival_time_flight fields ---  是空白 但在 var_dump中，结果值为00:00 我的问题是如何解决空白问题？