views/layouts/content.php

content.php

<?php
use yii\widgets\Breadcrumbs;
use dmstr\widgets\Alert;

?>
<div class="content-wrapper">
    <?=
    Breadcrumbs::widget(
        [
            'links' => isset($this->params['breadcrumbs']) ? $this->params['breadcrumbs'] : [],
        ]
    ) ?>

    <section class="content">
        <?= Alert::widget() ?>
        <?= $content ?>
    </section>
</div>
…