dynamic dependent select box using JQuery and Ajax Issue

Question

I have a problem with my dynamic dependent select box which I have been trying to solve since morning and I couldn't still solve it. The first select box gets all the regions from the database but the second select box doesn't respond to the first one value and returns nothing, which I really don't know why? I have checked everything including my form, my php code, my database and my scripts and still don't know what is happening. Any help?

Here is my form

<form action="" enctype="multipart/form-data"  method="post">
        <div class="grid-2">
            <div>
                <div class="line" style="width: 105%;">
                    <label class="label" for="regionId">Region *</label>
                    <div class="selectWrapper">
                        <select class="select " id="region" name="regionId">
                            <option value="">S&eacute;lectionner la Region</option>
                            <?php
                                  $getRegion = $region->getAllRegion();
                                  if($getRegion){
                                    while($result = $getRegion->fetch_assoc()){
                              ?>
                            <option value="<?php echo $result['regionId']; ?>"><?php echo $result['regionName']; ?></option>
                            <?php } } ?>
                        </select>
                    </div>
                </div>
            </div>
            <div>
                <div class="line" style="width: 105%;">
                    <label class="label" for="townId">Ville *</label>
                    <div class="selectWrapper">
                        <select class="select" id="town" name="townId">
                            <option value="">Select Region first</option>
                        </select>
                    </div>
                </div>
            </div>
        </div>

        <div class="line">
                    <label class="label" for="phone">T&eacute;l&eacute;phone *</label>
                    <input type="text" class="input full" name="phone" value=""/>

        </div>

        <div class="line">
            <label class="label" for="Email">Adresse email *</label>
            <input type="text" class="input full" name="email" value="" />

        </div>

    <center><input type="submit" id="create_store_button" class="button-blue full mtm" value="Reserver"></center>

Here is my Ajax Fetch.php

<?php
 include '../lib/session.php'; 
 include '../lib/database.php';
 include '../helpers/format.php';
 include '../helpers/format2.php';

 spl_autoload_register(function($class){
    include_once "../classes/".$class.".php";
     });

 $db = new Database();
 $fm = new Format();
 $region = new Region();

  if(!empty($_POST["regionId"])){

 $getTown = $region->getAllTown();
  if($getTown){
    echo '<option value="">Select Town</option>';
    while($result = $getTown->fetch_assoc()){
        echo '<option value="'.$result['townId'].'">'.$result['townName'].'</option>';
    }
}else{
    echo '<option value="">Town not available</option>';
}
 }

?>

Here is my Javascript

    <script>
    $(document).ready(function(){
    $('#region').on('change',function(){
        var regionID = $(this).val();
        if(regionID){
            $.ajax({
                type:'POST',
                url:'fetch.php',
                data:'regionId='+regionID,
                success:function(html){
                    $('#town').html(html);
                }
            }); 
        }else{
            $('#town').html('<option value="">Select Region first</option>');
        }
    });

</script>

Here is my PHP Class

            <?php 
            $filepath = realpath(dirname(__FILE__));
            include_once ($filepath.'/../lib/database.php');
            include_once ($filepath.'/../helpers/format.php');
        ?>

        <?php
        class Region{

            private $db;
            private $fm;

            public function __construct(){
                $this->db = new Database();
                $this->fm = new Format();
            }

            public function getAllRegion(){
                $query = "SELECT * FROM region ORDER BY regionId";
                $result = $this->db->select($query);
                return $result;
            }

            public function getAllTown(){
            $query = "SELECT * FROM town WHERE regionId = ".$_POST['regionId']." ORDER BY townName ASC";
            $result = $this->db->select($query);
            return $result;
            }

        }
        ?>