## 思路 一：獲取 `parent_id`，默認為0 二：查詢全部菜單， 三：`foreach` 形成帶有 `selected` 的新數組 四：用 `Tree` 類形成帶有樹形結構結構的內容 五：賦值 ## 代碼 ``` <?php namespace app\agent\controller; use think\Controller; use think\Db; use tree\Tree; class MenuController extends Controller { /** * 后臺菜單添加 */ public function add() { $tree = new Tree(); $parentId = $this->request->param("parent_id", 0, 'intval'); $result = Db::name('AdminMenu')->order(["list_order" => "ASC"])->select(); $array = []; foreach ($result as $r) { $r['selected'] = $r['id'] == $parentId ? 'selected' : ''; $array[] = $r; } $str = "<option value='\$id' \$selected>\$spacer \$name</option>"; $tree->init($array); $selectCategory = $tree->getTree(0, $str); $this->assign("select_category", $selectCategory); return $this->fetch(); } } ``` ## 要點解析 如圖所示，這里是關鍵，形成一個帶`selected` 的新數組