yii2 gridview select column
<?=Html::beginForm(['controller/bulk'],'post');?>
<?=Html::dropDownList('action','',[''=>'Mark selected as: ','c'=>'Confirmed','nc'=>'No Confirmed'],['class'=>'dropdown',])?>
<?=Html::submitButton('Send', ['class' => 'btn btn-info',]);?>
<?=GridView::widget([
'dataProvider' => $dataProvider,
'columns' => [
['class' => 'yii\grid\CheckboxColumn'],
...
],
]); ?>
<?= Html::endForm();?>