How to add a class in Yii2 if the page is not the main one for example?

Question

Yii

Good afternoon, please tell me how to add a class in Yii2 if the page is not the main one, for example?

Is there a class <div class="header"></div>
how to add a class to the header if we are not on the main page?
to become like this:<div class="header header2"></div>

Answer 1

<?php if (\Yii::$app->request->baseUrl == '/'): ?>
    <div class="header"></div>
<?php else: ?>
    <div class="header header2"></div>
<?php endif ?>