<script>
 
var sid  = {SID};
var remove_zone = {SID_REMOVE};
 
$("#answer229618X650X26215").change(function() {
 
    var region = $(this).val();
 
    $("#answer"+remove_zone+ "option").remove();
        $("#answer"+zone).html("<option value='' selected='selected'>Text placeholder example..</option>");
 
    $.ajax({
      type: "GET",
      url: "http://you_url/get_zones.php",
      data: "id_region="+region,
    }).done(function (zone){
 
 
            $.each(zone, function(i) {
                $('#answer'+remove_zone).append("<option value=\""+zone[i].codigo_zone+"\">"+zone[i].zone+"<\/option>");
            });
    });
  });
</script>
 
 

<?php 
require 'database.php';
 
$region = $_GET['id_region'];
 
$sql = "SELECT code_zone,zone FROM zones where id_region = $region";
 
$result = mysqli_query($con,$sql);
 
header('Content-Type: application/json');
 
 
$j = array();
 
while ($row = mysqli_fetch_array($result)) 
{
  $j[] = $row;
}
 
echo json_encode($j);
 
mysqli_close($con);
?>