How to get the value of a select input in Phalcon?

Question

I have a small form with a select input and a textarea for commenting. I want to make the textarea required only if the value of the select input is 1, for example, otherwise, it shouldn't be required. How can I accomplish this, is there a way to get the value of the select input once the user has clicked on one of the options ? Here's my CommentForm.php :

$this->add(new Select(
    'active',
    [
        1 => 'Something',
        0 => 'Something else'
    ],
));

$comment = new TextArea('comment', [
    'placeholder' => 'comment ...'
]);
$comment->addValidators([
    new PresenceOf([
        'message' => 'Comment is required'
    ])
]);
$this->add($comment);

This is how I render it in the volt file :

{{ form() }}
  <div class="modal-body">
      <div class="form-group">
          <label>Select</label>
          <div class="input-group">
              <div class="input-group-prepend">
                  <span class="input-group-text"><i class="fas fa-comment-alt"></i></span>
              </div>
              {{ formComment.render("active", ["class": "form-control"]) }}
            
          </div>
      </div>

      <div class="form-group">
          <label>Comment</label>
          <div class="input-group">
              <div class="input-group-prepend">
                  <span class="input-group-text"><i class="fas fa-comment-alt"></i></span>
              </div>
              {{ formComment.render("comment", ["class": "form-control"]) }}
          </div>
      </div>
  </div>
  <div class="modal-footer">
      <input type="hidden" name="typeID" value="13">
      {{ submit_button("addComment", 'name':'addComment', "class": "btn btn-success", 'value':'submit') }}
      {{ formComment.render('csrf', ['value': security.getToken()]) }}
  </div>
{{ end_form() }}

Thanks in advance!