I’m encountering trouble with POST [closed]

I always get this error whenever I submit ”
Warning: Undefined array key “seats” in C:xampphtdocsLaCineReservabooking.php on line 30

Warning: foreach() argument must be of type array|object, null given in C:xampphtdocsLaCineReservabooking.php on line 34
” I don’t know why it always say null even if I checked some boxes.

This is the code I’ve used for this.

if(isset($_POST["btn_booking"]))
{
    // include("checkSeat.php");
    $con=new connec();

    $cust_id=$_POST["cust_id"];
    $show_id=$_POST["show_id"];
    $no_tikt=$_POST["no_ticket"];
    $bkng_date=$_POST["booking_date"];
    $total_amnt=(600 * $no_tikt);

    $bookedSeats = $_POST['seats'];

    $data = array();

    foreach($bookedSeats as $seat)
    
    $data[] = addslashes($seat);
    
    $data = implode("," , $data);

    $sql="insert into seat_reserved values(0,$show_id,$cust_id,'$data','true')";
    $abc= $con->insert_lastid($sql);

    $sql="insert into seat_detail values(0,$cust_id,$show_id,$no_tikt)";
    $seat_dt_id=$con->insert_lastid($sql);


    $sql="insert into booking values(0,$cust_id,$show_id,$no_tikt,$seat_dt_id,'$bkng_date',$total_amnt)";
    $con->insert($sql,"Your Ticket is Booked");
}

<div class="row">
    <form method="POST">
         <table style="width:100%;color:white;">
<tr>
   <td>A</td>
     <td><input type="checkbox" name="seats[]" value="A-01" onclick="checkboxtotal()" <?php checkme("A-01",$ajaycomma); ?>></td>
     <td><input type="checkbox" name="seats[]" value="A-02" onclick="checkboxtotal()" <?php checkme("A-02",$ajaycomma); ?>></td>
    <td><input type="checkbox" name="seats[]" value="A-03" onclick="checkboxtotal()" <?php checkme("A-03",$ajaycomma); ?>></td>
                            
</tr>

      </table>
    </form>
  </div>