代码展示：
将Tree树类放入扩展目录 \extend\Tree\Tree.php
//引入Tree
use Tree\Tree
//所有数据
$cate = Db::name('category')->where(['status'=>1])->order('listorder asc')->selected();
$tree = new Tree; //实例化
$tree->tree($sort); //调用tree方法
$tree->icon = array(' │ ', ' ├─ ', ' └─ '); //树结构字符串
$list=$tree->getArray(); //获取树结构文件下载：Tree.zip
