Repopulate dropdown

codeigniter how to populate second dropdown list based on the first one using codeigniter

Just convert it to CodeIniter 4.

Maybe im missing something but here is my code for drop down population. Plz any ideas?

//Get rack from warehouse
    public function get_rack_by_warehouse($id){
        $rack = $this->warehouse_model->get_rack_by_warehouse($id);
            foreach($rack as $key => $r){
                echo '<option value="'.$r['rack_id'].'">'.$r['name'].'</option>';
            }
   
    }


On view i have this code:

<script type="text/javascript">

function get_rack(warehouse_id){
    $.ajax({
        url:        '<?php echo base_url();?>warehouse/function get_rack_by_warehouse/' + warehouse_id,
        success:    function(response){
            jQuery('#rack_id').html(response);
        }

    });
}

</script>