How to return an ActiveForm from an anonymous function in YII2?

Question

Yii

When rendering the GridView, it is necessary to display an "update" button along with a modal window with an ajax edit form.
To display the column I use the following code:

[
  'class'    => yii\grid\ActionColumn::className(),
  'template' => '{view} {update} {delete}',
  'buttons'  => [
    'update' => function ($url, $model, $key) {
        $html = [];
        $html[] = Modal::begin([
          'toggleButton' => ['label' => 'update', 'class' => 'btn btn-primary'],
        ]);
        $html[] = $form = ActiveForm::begin([
          'options'     => [
            'data-pjax' => true,
          ],
        ]);
        $html[] = $form->field($model, 'id')->textInput();
        // всякие поля формы
        $html[] = ActiveForm::end();
        $html[] = Modal::end();

        return implode("\n", $html);
    }
]

An error occurs: PHP Fatal Error - yii\base\ErrorException - Object of class yii\bootstrap\ActiveForm could not be converted to string.
How to correctly display the HTML code of the form from the function?

Answer 1

I use ob_start()...etc.
A simple implementation, but a little bit unreadable, so I cover such comment blocks.

Answer 2

ActiveForm and Modal are descendants of Widget, which has a render() method that returns html, I would dig in this direction

Answer 3

$this->render()