Как отобразить текущую категорию в дереве категорий Codeigniter

Question

У меня есть контроллер, отображающий рекламу по категориям и подкатегориям ...

    public function cat( $cat_alias, $subcat_alias = null)
        {

            $where = array( 'catalogue' => $cat_alias );
            $ad_category = $this->Site_model->get_single( 'categories' , $where );
            $children = $this->Site_model->get_childrens($ad_category->id);

            foreach ($children as $child) 
            {
                $childs[] = $child->id;
            }


            if ( !empty( $ad_category ) )
            {

                if (!empty($subcat_alias)) 
                    {

                    $where = array( 'catalogue' => $subcat_alias );
                    $ad_subcategory = $this->Site_model->get_single( 'categories' , $where );

                    $where = array('category_id' => $ad_subcategory->id);

                    }

                    else
                    {

                    $where = array( 'category_id' => $childs );

                    }

                $ads = $this->Site_model->get( 'ads' , $where );



                if ( !empty( $ads ) )
                {

                    foreach ( $ads as $ad )
                    {
                        $ad_ids[] = $ad->id;
                    }

                    $where = array( 'id' => $ad_ids );
                    $data['ads'] = $this->Site_model->get( 'ads' , $where );

                    $data['categories'] = $this->Site_model->get_categories();
                    $this->load->view( 'cat' , $data );

                }
                else
                {
                    $this->session->set_flashdata( 'alert' , 'There are no ads in this category.' );
                     redirect( '/' );
                }

            }
            else
            {
                $this->session->set_flashdata( 'alert' , 'Invalid category name.' );
                 redirect( '/' );           
            }

        }

И у меня есть функции в модели, которые отображают дерево категорий

public function get_categories()
    {
        $this->db->where('parent_id', 0);
        $this->db->order_by('on_homepage', 'asc');
        $query = $this->db->get('categories');
        $return = array();

        foreach ($query->result() as $category)
        {
            $return[$category->id] = $category;
            $return[$category->id]->subs = $this->get_sub_categories($category->id); // Get the categories sub categories
        }

        return $return;
    }


    public function get_sub_categories($category_id)
    {
        $this->db->where('parent_id', $category_id);
        $this->db->order_by('on_homepage', 'asc');
        $this->db->limit(5);
        $query = $this->db->get('categories');
        return $query->result();
    }

И в представленииЯ отображаю дерево категорий

    <?php foreach ($categories as $category): ?>
    <?php echo $category->name; ?>
    <?php
        if(!empty($category->subs)) { 
            echo '<ul>';
            foreach ($category->subs as $sub)  {
                echo '<li><a href="'. base_url() . $sub->full_catalogue .'">' . $sub->name . '</a></li>';
            }
            echo '</ul>';
        }
    ?>

Я не знаю, как изменить это дерево вместе, когда я перемещаюсь по разным категориям, так что категория, в которой я сейчас нахожусь, выбрана.

И база данных ...

CREATE TABLE `categories` (
  `id` int(11) NOT NULL,
  `name` tinytext CHARACTER SET utf8 COLLATE utf8_polish_ci NOT NULL,
  `catalogue` tinytext CHARACTER SET utf8 COLLATE utf8_polish_ci,
  `full_catalogue` varchar(140) CHARACTER SET utf8 COLLATE utf8_polish_ci DEFAULT NULL,
  `on_homepage` int(2) NOT NULL DEFAULT '0',
  `lvl` tinyint(4) NOT NULL DEFAULT '0',
  `parent_id` smallint(6) NOT NULL DEFAULT '0'
) ENGINE=MyISAM DEFAULT CHARSET=latin2;


INSERT INTO `categories` (`id`, `name`, `catalogue`, `full_catalogue`, `on_homepage`, `lvl`, `parent_id`) VALUES
(1, 'Praca', 'praca', 'praca', 1, 1, 0),
(2, 'Motoryzacja', 'motoryzacja', 'motoryzacja', 2, 1, 0),
(4, 'Nieruchomości', 'nieruchomosci', 'nieruchomosci', 3, 1, 0),
(5, 'Dam pracę', 'dam-prace', 'praca/dam-prace', 1, 2, 1),
(8, 'Imprezy i wydarzenia', 'imprezy', 'imprezy', 12, 1, 0),
(9, 'Usługi', 'uslugi', 'uslugi', 13, 1, 0),
(16, 'Turystyka', 'turystyka', 'turystyka', 4, 1, 0);




CREATE TABLE `ads` (
  `id` int(11) NOT NULL,
  `category_id` int(11) NOT NULL DEFAULT '0',
  `city_id` smallint(6) NOT NULL DEFAULT '0',
  `user_id` int(11) NOT NULL,
  `off_id` smallint(6) DEFAULT '0',
  `title` text CHARACTER SET utf8 COLLATE utf8_polish_ci NOT NULL,
  `description` longtext CHARACTER SET utf8 COLLATE utf8_polish_ci NOT NULL,
  `price` bigint(9) DEFAULT '0',
  `contact` tinytext CHARACTER SET utf8 COLLATE utf8_polish_ci,
  `email` tinytext CHARACTER SET utf8 COLLATE utf8_polish_ci,
  `phone` tinytext CHARACTER SET utf8 COLLATE utf8_polish_ci,
  `photo1` tinytext CHARACTER SET utf8 COLLATE utf8_polish_ci,
  `photo2` tinytext CHARACTER SET utf8 COLLATE utf8_polish_ci,
  `photo3` tinytext CHARACTER SET utf8 COLLATE utf8_polish_ci,
  `user_ip` varchar(16) CHARACTER SET utf8 COLLATE utf8_polish_ci NOT NULL,
  `promoted` int(1) NOT NULL DEFAULT '0',
  `promoted_end_date` int(11) NOT NULL DEFAULT '0',
  `active` tinyint(4) DEFAULT '0',
  `activate_code` varchar(24) CHARACTER SET utf8 COLLATE utf8_polish_ci NOT NULL,
  `views` int(11) NOT NULL DEFAULT '0',
  `created` int(11) NOT NULL,
  `updated` int(11) NOT NULL DEFAULT '0'
) ENGINE=MyISAM DEFAULT CHARSET=latin2;