yii, recursive function to create category sub category hierarchy

Create this function in the category model file:

--------------------------------------------------------------------------------- 

<?php
public function get_category_hr($cat_id, $selected_cat_id, $level_string) {
        
       
        $select_str='';
       
        if(!$level_string)
              {
                  $level_string='';
              }
       
       
        if ($cat_arr = $this->findAll('category_parent_id=' . $cat_id)) {
           

            foreach ($cat_arr as $cat) {
               
                $select_str.="<option value={$cat->category_id}";
                if($selected_cat_id==$cat->category_id)
                    $select_str.= ' selected';
                $select_str.=">{$level_string}{$cat->category_name}</option>";
                                   
                    $select_str.= $this->get_category_hr($cat->category_id, $selected_cat_id, $level_string.'+');
                                       
               
            }
           
           
           
        }
        else
        {
            return false;
        }
       
        return $select_str;
       
    }
?>

 Call this function like this:

-------------------------------------------

    <select name='Categories[category_parent_id]'>

            <option value='0'>No Parent</option>

            <?php

                    echo $Categories::model()->get_category_hr(0, $model->category_parent_id, '');

            ?>

            </select>

That should be all.