[php] How to make a drop down list in yii2?

There are some good solutions above, and mine is just a combination of two (I came here looking for a solution).

@Sarvar Nishonboyev's solution is good because it maintains the creation of the form input label and help-block for error messages.

I went with:

<?php
use yii\helpers\ArrayHelper;
use app\models\Product;
?>
<?=
$form->field($model, 'parent_id')
     ->dropDownList(
            ArrayHelper::map(Product::find()->asArray()->all(), 'parent_id', 'name')
            )
?>

Again, full credit to: @Sarvar Nishonboyev's and @ippi