yii2中怎么输出二级菜单，根据我自己的样式建立的二级菜单

CREATE TABLE `category` (
  `id` int(50) NOT NULL,
  `name` varchar(50) COLLATE utf8_vietnamese_ci NOT NULL COMMENT '分类名称',
  `pid` int(11) NOT NULL DEFAULT '0' COMMENT '父级分类id',
  `url` varchar(50) COLLATE utf8_vietnamese_ci NOT NULL COMMENT '访问地址',
  `status` int(2) NOT NULL DEFAULT '1' COMMENT '状态',
  `created_at` int(12) NOT NULL COMMENT '创建时间',
  `updated_at` int(12) NOT NULL COMMENT '修改时间'
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_vietnamese_ci;

--
-- 转存表中的数据 `category`
--

INSERT INTO `category` (`id`, `name`, `pid`, `url`, `status`, `created_at`, `updated_at`) VALUES
(1, 'cyg', 0, 'www.baidu.com', 1, 1645603515, 1645603515),
(2, 'liwen', 1, 'www.bauc.om', 1, 1645604857, 1645604857);

<?php
namespace backend\helpers;
class Tree
{
	public static function getTree($list,$pid=0)
	{
		$tree=[];
		foreach($list as $row)
		{
			if($row['pid']==$pid)
			{
				$tree[$row['id']]=$row;
				$children=self::getTree($list,$row['id']);
				$children&&$tree[$row['id']]['children']=$children;
			}
		}
		return $tree;
	}
	public  static function getTrees($list,$pid=0,$level=0)
	{
		static $tree=[];
		foreach ($list as $k => $row) {
			if($row['pid']==$pid)
			{
			$row['name']=html_entity_decode(str_repeat("&nbsp;&nbsp;",$level))."|--".$row['name'];
			$tree[$row['id']]=$row;
			unset($list[$k]);
			self::getTrees($list,$row['id'],$level+1);
		}
		}
		return $tree;
	}
	
}

<?php

use yii\helpers\Html;
use yii\widgets\ActiveForm;
/* @var $this yii\web\View */
/* @var $model backend\models\Category */
/* @var $form yii\widgets\ActiveForm */
$list=\backend\models\Category::find()->asArray()->all();
$tree=\backend\helpers\Tree::getTrees($list);
$tree=\yii\helpers\ArrayHelper::map($tree,'id','name');
array_unshift($tree,Yii::t('backend','parent'));
?>

<div class="category-form">

    <?php $form =ActiveForm::begin(); ?>

   <?= $form->field($model, 'id')->textInput() ?>

    <?= $form->field($model, 'name')->textInput(['maxlength' => true]) ?>

    <?= $form->field($model, 'pid')->dropDownList($tree) ?>

    <?= $form->field($model, 'url')->textInput(['maxlength' => true]) ?>

    <?= $form->field($model, 'status')->radioList(\backend\models\Category::getStatusArray()) ?>

    <?= $form->field($model, 'created_at')->textInput() ?>

    <?= $form->field($model, 'updated_at')->textInput() ?>

    <div class="form-group">
        <?= Html::submitButton(Yii::t('app', 'Save'), ['class' => 'btn btn-success']) ?>
    </div>

    <?php ActiveForm::end(); ?>

</div>

<ul class="nav">

                <?php  $list=\backend\models\Category::find()->asArray()->all();
                    $categorys=\backend\helpers\Tree::getTree($list);
                ?>
                <?php  foreach($categorys as $category):?>
                    <li><a href="about.html"><?= $category['name']?></a>
                       <?php  foreach($category['children'] as $aa):?>
                        <ul class="two">
                            <li><a href="about.html"><?= $aa['name']?></a></li>
                        </ul>
                         <?php endforeach;?>
                    </li>
                <?php endforeach;?>
                </ul>