How to set up composite forms in Yii2?

Question

PHP

I follow the instructions as here https://github.com/ElisDN/yii2-composite-form

class EditForm extends CompositeForm
{
public function __construct(int $moduleID, $config = [])
{
....
$ageModels = ChildrenAges::find()->all();

        $this->ages = array_map(function (ChildrenAges $ageModel) {
            return new AgeForm($ageModel);
        }, $ageModels);
....
}
....

    protected function internalForms()
    {
        return ['ages'];
    }
}

when editing, all records are inserted into the fields, but when adding new records
after

if (request()->isPost && $model->load(request()->post()) && $model->validate()) {

$model->ages is empty even though there is
AgeForm data in $_POST => [
0 => [...],
1 => [...]
]