How to set tree view in dynamic menu in codeigniter

Hello guyyz i need help in design,i don't have ideas about design, i have created dynamic menu in codeigniter i want to set that menu in treeview. First click on parent menu after open child menus, so how to implement it help me

Here is My View Code:

  <?php
                                        foreach ($test as $val) {
                                            $array = explode(",", $val->category_id);
                                        }

                                        foreach ($get_cat as $key => $value) {

                                            if (in_array($value->category_id, $array)) {
                                                echo $value->category_name . '&nbsp;&nbsp;'; //Here my menu print
                                            }
                                        }
             ?>