'buttons' => [
  'update' => function ($url, $model, $key) {
       return Html::a('<span class="glyphicon glyphicon-pencil"></span>', '#', [
          'data-toggle' => 'modal',
          'data-target' => '#update-modal',
          'class' => 'data-update',
          'data-id' => $key,
          'title'=>'更改状态',
          ]);
        },
      ],   

<?php
use yii\bootstrap\Modal;//模态弹出框
Modal::begin([
  'id' => 'update-modal',
  'header' => '<h4 class="modal-title">更改状态</h4>',
  'footer' => '<a href="#" rel="external nofollow" class="btn btn-primary" data-dismiss="modal">Close</a>',
]); 
Modal::end();
?>

<?php    
$requestUpdateUrl = Url::toRoute('update');
$updateJs = <<<JS
  $('.data-update').on('click', function () {
    $.get('{$requestUpdateUrl}', { id: $(this).closest('tr').data('key') },
      function (data) {
        $('.modal-body').html(data);
      } 
    );
  });
JS;
$this->registerJs($updateJs); 
?>

 public function actionUpdate($id)
{
  $model = Order_packet::findOne($id);
  $model->setScenario('update');//指定场景，防止时间等变量同时被更改
  if ($model->load(Yii::$app->request->post()) && $model->save()) {
    return $this->redirect(['index']);
  } else {
    return $this->renderAjax('update', [  //这里需要渲染update模版，要在view中写update
      'model' => $model,
    ]);
  }
}