AJAX and jQuery - binding more than one tag

[eluser]Jason Tan Boon Teck[/eluser]
I am trying to make a dynamic drop down list with more than 2 tiers. I have managed to get the last 2 tiers working with AJAX and jQuery, i.e. selecting a Drug Formulary will retrieve via AJAX a list of trade names to select.

Codes that work.
Main view:

Code:

...
// Set for AJAX calling
$siteurl    =   site_url()."/ehr_ajax/get_prescription_drugtradenames";
//echo $siteurl;
?>
[removed]
    $(document).ready(function() {
      $('#drug_formulary_id').change(function (){
            ajax_trade_name()}
        );
        return false;
      })


    function ajax_trade_name() {
        var siteurl = "<?php echo $siteurl; ?>";
        var ajax_drug_formulary_id = $('#drug_formulary_id').val();
        var data = 'ajax_drug_formulary_id=' + ajax_drug_formulary_id;
        //alert(siteurl+' '+data);
        $.ajax({
          type:'POST',
          url:siteurl,
          data: data,
          success: function (result) {
            $('#message').html(result);
          }
        }
    )}

Controller:

Code:

function get_prescription_drugtradenames()
    {
        $data['ajax_drug_formulary_id'] = $_POST['ajax_drug_formulary_id'];  //set the record ID
        //$data['patient_id'] = $this->uri->segment(3);

        $data['tradename_list'] = $this->memr_rdb->get_tradename_by_formulary($data['ajax_drug_formulary_id']);
        $this->load->vars($data);

        $this->load->view("ehr/ajax_get_prescription_drugtradenames");
    }

AJAX view ajax_get_prescription_drugtradenames.php:

Code:

echo "\n<select name='drug_code_id' class='normal' id='tradename'>";
        echo "\n<option value='' >Some examples of this drug</option>";
        foreach($tradename_list as $tradename_item)
        {
            echo "\n<option value='".$tradename_item['drug_code_id']."' ";
            if(isset($drug_code_id)) {
                echo ($drug_code_id==$tradename_item['drug_code_id'] ? "selected='selected'" : "");
            }
            echo ">".$tradename_item['trade_name']."&nbsp;[".$tradename_item['drug_code']."]</option>";
        }
    echo "</select>";

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