Embedded documents behavior(https://github.com/consultnn/yii2-mongodb-embedded)
echo $form->field($model, 'phones', ['options' => ['class' => 'col-lg-6 col-sm-6']])->widget(
\consultnn\widgets\MultiEmbedded::className(),
[
'form' => $form,
'embeddedModelClassName' => \common\models\Phone::className(),
'embeddedFormName' => Html::getInputName($model, 'phones')
]
);