Can somebody please explain to me what is the right way to call a php function with jquery / ajax in Codeigniter. Right now, this code isn't working and i cant figure out whay. Note that admin.php controler is inside admin map. Thanks in advance

html code

<form action=# method=POST id=change>

             <input type=hidden value=<?php echo $row->id_product; ?> id=prod >    

             <input type=submit value=switch >

</form>

<div class=resultdiv>

    <?php echo $data; ?>

</div>

my function inside admin.php controller

 public function do_search(){

        $id = $this->input->post('id');

        return $id;

    }

Jquery AJAX script

$( #change ).submit(function() {

  alert( Change );

  var id = $('#prod').val();

     $.ajax({

            type:'POST',

            url:'admin321/do_search',

            data:{'id':id},

            success:function(data){

                $('#resultdiv').html(data);

            }

        });

});

Config / routes.php

$route['admin/do_search'] = admin_controller/admin/do_search;