I want to insert values of multiple checkbox into diffrent rows in table

The problem is there is an enquiry page which contains multiple checkboxes, date, client name and so on and there are 2 tables main_enquiry and sub_enquiry. what i need to do is when i insert an enquiry into main_enquiry table the same enquiry id along with the selected checkboxes(the checkboxes are dynamically called from another table) need to be inserted into sub_enquiry table in different rows but with same enquiry id. i'm using php to do this

i tried with many answers in stackoverflow but can't find a solution.

`if (isset($_POST['submit'])) 
 {
$cli=$_POST['serv'];
$dt=$_POST['date'];
$rq=$_POST['requiremnts'];
$fi=$_FILES['file']['name'];
move_uploaded_file($_FILES['file']['tmp_name'], "attachments/".$fi);
$path="attachments/".$fi;
$sqlenq=mysql_query("insert into tbl_enquiry (client_id,enquiry_date,enquiry_requirement) values ('$cli','$dt','$rq')");
if ($insid=mysql_insert_id()) 
{
  $sqlenqsel=mysql_fetch_array(mysql_query("select * from tbl_enquiry where enquiry_id='$insid'"));
  $enq=$_POST['enqid'];
  $check=$_POST['subenq'];
  foreach ($check as $value)
  {
    $sqlsubenq=mysql_query("insert into tbl_sub_enquiry set enquiry _id='$enq',enq_categories='$serv'");
  }
}
}`



 `<div class="col-12 col-sm-5 col-lg-5">
  <?php
  while ($showcat=mysql_fetch_array($cat))
   {
   ?>
   <label class="custom-control custom-checkbox custom-control-inline">
   <input type="checkbox" checked="" class="custom-control-input" 
   name="subenq"><span class="custom-control-label" value="<?php echo 
   $showcat['services_category_id'];?>"><?php echo 
    $showcat['services_category_name'];?></span>                                          
    </label>
     <?php } ?>
      </div>`

if there is a more easier way then that is preferred.