[ASK - URGENT]Combobox dinamis dari database

CREATE TABLE IF NOT EXISTS `cities` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `province_id` int(11) NOT NULL,
  `city` varchar(32) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=5 ;
INSERT INTO `cities` (`id`, `province_id`, `city`) VALUES
(1, 1, 'bandung'),
(2, 2, 'surabaya'),
(3, 1, 'cimahi'),
(4, 2, 'bla blaa');
CREATE TABLE IF NOT EXISTS `provinces` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `province` varchar(32) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `province` (`province`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=3 ;
INSERT INTO `provinces` (`id`, `province`) VALUES
(1, 'jabar'),
(2, 'jatim');

class Location extends Model {
  public function __construct() {
    parent::__construct();
  }
 
  public function getCity($province_id) {
    return $this->db->get_where('cities', array('province_id'=>$province_id));
  }
 
  public function getAllProvince() {
    return $this->db->get('provinces');
  }
}

class Welcome extends Controller {
 
	function Welcome()
	{
		parent::Controller();	
		$this->load->model('location');
	}
 
	function index()
	{
		$t = $data['provinces'] = $this->location->getAllProvince();
		$this->load->view('welcome_message', $data);
	}
 
	function getCity()
	{
    $province_id = $this->input->post('province_id');
    $cities = $this->location->getCity($province_id);
    echo '<ul>';
    foreach ($cities-&gt;result() as $city) {
      echo "<li>{$city->city}</li>";
    }
    echo '</ul>';
	}
}

<script src="<?php echo base_url()?>js/jquery.js"></script>
<script>
  $().ready(function(){
    $('select').change(function(){
      var data = $('form').serialize();
      $.post('<?php echo site_url('welcome/getCity') ?>', data, function(response){
        $('#city').html(response);
      })
    })
  })
</script>
<form method="post">
  <select name="province_id">
  <?php foreach ($provinces->result() as $v): ?>
    <option value="<?php echo $v->id ?>"><?php echo $v->province ?></option>
  <?php endforeach ?>
  </select>
  <div id="city"></div>
</form>

system
-- application
-- <strong>js </strong>