URL in Yii2 GridView
solution:
<?= GridView::widget([ 'dataProvider' => $dataProvider, 'filterModel' => $searchModel, 'columns' => [ ['class' => 'yii\grid\SerialColumn'], [ 'label'=>'bla', 'format' => 'raw', 'value'=>function ($data) { return Html::a(['site/index']); }, ], ['class' => 'yii\grid\ActionColumn'], ],]); ?>