yii2 gradview 输出当前时间和图片

<?= 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',],
],

]); ?>