echo Nav::widget([
        'options' => ['class' => 'navbar-nav navbar-right'],
        'items' => [
            ['label' => 'Home', 'url' => ['/site/index']],
            ['label' => 'About', 'url' => ['/site/about']],
            ['label' => 'Contact', 'url' => ['/site/contact']],
            Yii::$app->user->isGuest ? (
                ['label' => 'Login', 'url' => ['/site/login']]
            ) : (
                '<li>'
                . Html::beginForm(['/site/logout'], 'post')
                . Html::submitButton(
                    'Logout (' . Yii::$app->user->identity->username . ')',
                    ['class' => 'btn btn-link logout']
                )
                . Html::endForm()
                . '</li>'
            )
        ],
    ]);