CODE EXAMPLE FOR PHP

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' => 'yiigridCheckboxColumn'],
        ...
     ],
  ]); ?>

<?= Html::endForm();?>