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

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!