yii2 gradview 输出当前时间和图片

gradview是一个表格显示控件；
columns是列选项
官方api：http://www.yiiframework.com/doc-2.0/yii-grid-gridview.html

<?= GridView::widget([ 'dataProvider' => $dataProvider, 'filterModel' => $searchModel, 'columns' => [ ['class' => 'yii\grid\SerialColumn'], ['label'=>'创建时间','attribute' => 'created_at','value'=>function($m){ return date("Y-m-d H:i:s",$m->created_at); }], ['label'=>'缩略图','format'=>'raw','value'=>function($m){ return Html::img($m->image_path,['alt' => '缩略图','width' => 80]); }], ['class' => 'yii\grid\ActionColumn',], ], ]); ?>