<?= GridView::widget([         'dataProvider' => $dataProvider,         //'filterModel' => $searchModel,         'columns' => [             ['class' => 'yii\grid\SerialColumn'],             //显示的字段             //code的值             ['attribute'=>'这是测试code','value'=>function(){return 'abc';}],             'name',             'population',                         ['class' => 'yii\grid\ActionColumn','header' => '操作',],             [                 'label'=>'更多操作',                 'format'=>'raw',                 'value' => function($data){                     $url = "http://www.baidu.com";                     return Html::a('添加权限组', $url, ['title' => '审核']);                 }             ]                ],     ]); ?>