jquery - populate a dropdown depending on first dropdown -

i want populate whoom-to-meet dropdown box after select department department-to-go dropdown box,but when click on department list departments show when choose department related employees department not showing in whoom-to-meet dropdown list. below 2 table. department table

+----+-----------+ | id | dept_name | +----+-----------+ |  2 |    hr     | +----+---------- + 

user_master table

+----+-------------+-----------+----------+ | id |  emp_name   |  dept_id  |   type   | +----+-------------+-----------+----------+ | 1  |   dipti     |     2     | employee | + ---+-------------+-----------+----------+ 

my controller

public function create_pass() {     $pageid = 1;     $data['hh'] = $this->admin_model->get_dept();     $this->load->view('header');     $this->load->view('sidebar');     $this->load->view('createpass', $data);     $this->load->view('footer'); }     public function select_item_by_dept() {     if ($this->session->userdata('admin_logged_in')) {         $category_id = $this->input->post('category_id');         $data['result'] = $this->admin_model->select_item_by_cat($category_id);          $html = "";                     foreach ($data['result'] $list) {             $html.="<option value='" . $list['dept_id'] . "'>" . $list['emp_name'] . "</option>";         }                    echo $html;     } else {         $this->load->view('login');     } } 

my model

function select_item_by_cat($category_id) {     $this->db->where('dept_id', '$category_id');     $query = $this->db->get('user_master');     return $query->result_array(); } function get_dept() {     $this->db->select("*");     $this->db->from('department');     $query = $this->db->get();     return $query->result_array(); } 

my view

<div class="form-group">   <label for="inputpassword3" class="col-sm-3 control-label">department go </label>   <div class="col-sm-3">     <select class="form-control select2" name="dptgo" id="dptogo" onchange="change_category(this.options[this.selectedindex].value)" style="width: 100%;">       <option selected="selected">select</option>                                                           <?php foreach($hh $datas)       { ?>         <option value="<?php echo $datas['id']; ?>"><?php echo $datas['dept_name']; ?></option> <?php } ?>     </select>     <div class="text-danger"><?php echo form_error('dptgo'); ?></div>   </div>   <label for="inputpassword3" class="col-sm-2 control-label">whom meet</label>   <div class="col-sm-4">     <select class="form-control select2" id="whomtmt" name="wtomeet" style="width: 100%;">       <option selected="selected">select</option>       <option></option>     </select>   </div> </div> 

my jquery

<script>   function change_category(category_id) {     if (category_id == "select") {       $("#whomtmt").html("<option>select</option>");       $("#whomtmt").trigger("chosen:updated");       $("#whomtmt").trigger("liszt:updated");     } else {       loaddata(category_id);     }   }   function loaddata(category_id) {     var datastring = 'category_id=' + category_id;     $.ajax({       type: "post",       url: "<?php echo site_url(); ?>/admin/select_item_by_dept",       data: datastring,       cache: false,       success: function (result) {         $("#whomtmt").html("<option>select</option>");         $("#whomtmt").append(result);         $("#whomtmt").trigger("chosen:updated");         $("#whomtmt").trigger("liszt:updated");       }     });   } </script> 

in model, in select_item_by_cat function

this wrong $this->db->where('dept_id', '$category_id');

the query executes

select * `user_master` `dept_id` = '$category_id' 

so change

$this->db->where('dept_id', $category_id); 

and try can helps :)