php通过前序遍历树实现无需递归的无限极分类

CREATE TABLE IF NOT EXISTS `category` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `title` varchar(50) NOT NULL,
 `lft` int(11) NOT NULL,
 `rgt` int(11) NOT NULL,
 `order` int(11) NOT NULL COMMENT '排序',
 `create_time` int(11) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=12 ;
--
-- 转存表中的数据 `category`
--
INSERT INTO `category` (`id`, `title`, `lft`, `rgt`, `order`, `create_time`) VALUES
(1, '顶级栏目', 1, 20, 1, 1261964806),
(2, '编辑后的分类', 16, 19, 50, 1264586212),
(4, '公司产品', 10, 15, 50, 1264586249),
(5, '荣誉资质', 8, 9, 50, 1264586270),
(6, '资料下载', 6, 7, 50, 1264586295),
(7, '人才招聘', 4, 5, 50, 1264586314),
(8, '留言板', 2, 3, 50, 1264586884),
(9, '总裁', 17, 18, 50, 1267771951),
(10, '新的分类的子分类', 11, 14, 0, 1400044841),
(11, 'PHP点点通-http://www.phpddt.com', 12, 13, 0, 1400044901);

<"lft - {$width}", FALSE)->where(array('lft >' => $category['rgt']))->update('category');
    $this->db->set('rgt', "rgt - {$width}", FALSE)->where(array('rgt >' => $category['rgt']))->update('category');
    echo 'delete success';
  }
  //编辑，
  public function edit()
  {
    //不用说了， 直接通过id编辑
    $id = 2;
    $this->db->update('category', array(
      'title' => '编辑后的分类'
    ), array(
      'id' => $id
    ));
    echo 'edit success';
  }
}