Chain Selection in Cakephp

ChainSelection.php

<?php
App::uses('AppController', 'Controller');
 
class CountriesController extends AppController {
         
    public $helpers = array('Js');
    public $components = array('RequestHandler');
    
    public function select() {
        $countries = $this->Country->find('list');
        
        $states = array();
        foreach ($countries as $country_id => $name) {
            $states = $this->Country->State->findByCountryId($country_id);
            break;
        }
        
        $this->set(compact('countries', 'states'));
    }
    
 
    public function states_list() {
        $this->request->onlyAllow('ajax');
        $id = $this->request->query('id');
        if (!$id) {
            throw new NotFoundException();
        }
 
        $states = $this->Country->State->find('list', array(
            'conditions' => array('country_id' => $id)
        ));
 
        $this->set(compact('states'));
        
    }
}

// select.ctp

<?php echo $this->Form->create('Country');?>
<?php echo $this->Html->script('states_ajax'); ?>
 
<fieldset>
    <legend><?php echo __('Countries and States');?></legend>
    <?php
        $url = $this->Html->url(array('controller' => 'countries', 'action' => 'states_list', 'ext' => 'json'));
        $empty = count($states) > 0 ? __('Please Select') : array('0' => __('No States Available'));
 
        echo $this->Form->input('country_id', array('id' => 'countries', 'rel' => $url, 'empty' => 'Choose Country'));
        echo $this->Form->input('state_id', array('id' => 'states', 'empty' => $empty));
    ?>
</fieldset>
<?php echo $this->Form->end(__('Submit'));?>

// Ajax Code

$(document).ready(function(){
    $("#states").attr("disabled","disabled");
    $("#countries").change(function(){
    $("#states").attr("disabled","disabled");
    $("#states").html("<option>Please wait...</option>");
    var id = $("#countries option:selected").attr('value');
 
    $.get("/countries/states_list", {id:id}, function(data){
        $("#states").removeAttr("disabled");
        $("#states").html(data);
        });
    });
   
});

please where is the states_ajax file in the $this->Html->script();