How to get value from select in yii2?

Question

Yii

I am making a basket ...
There is such a construction:

<p>
  <input type="number" data-id="qty" value="1" id="qty">
  <a href="<?= Url::to(['cart/add', 'id' => $product->id]) ?>" data-id="<?= $product->id ?>" class="btn btn-default add-to-cart"><i class="fa fa-shopping-cart"></i> <?= Yii::t('app', 'Add to cart') ?></a>
</p>

Quantity field and add to cart button.
The quantity data is transferred perfectly and everything is saved where necessary, but ... it also eats attributes that the user must specify.
I decided to make a select:

<?php foreach ($attributes as $attribute): ?>
<p>
<?= $attribute->content->name ?>: 
<?php if ($attribute->getValuesCount() == 1): ?>
  <?php foreach ($attribute->values as $val): ?>
    <?= $val->content->name ?>
  <?php endforeach ?>
<?php else: ?>
  <select data-id="val" id="val" name="val[]">
    <option value="">
      Select one
    </option>
<?php foreach ($attribute->values as $val): ?>
  <option value="<?= $val->id ?>">
    <?= $val->content->name ?>
  </option>
<?php endforeach ?>
  </select>
<?php endif ?>
</p>
<?php endforeach ?>

But the select value is not passed...
I tried both the checkbox and the radio, and also framed it with the form tag - no effect...
Everything seems to be simple, but something is clearly wrong
. Tell me, please, where to dig or what example, and then nowhere