在Yii2中，无法在网格视图中显示模型中的自定义列

public function getFormattedCreatedAt()
{
    return date('Y-m-d H:i:s', $this->created_at);
}

<?= GridView::widget([
    'dataProvider' => $dataProvider,
    'columns' => [
        'id',
        'name',
        'email',
        [
            'attribute' => 'created_at',
            'value' => function($model) {
                return $model->getFormattedCreatedAt();
            }
        ],
        'status',
        ['class' => 'yii\grid\ActionColumn'],
    ],
]); ?>