Use bootstrap menu in Yii with CMenu

bootstrap-cmenu-yii.php

<nav class="navbar navbar-default top-navbar" role="navigation">
	<div class="navbar-header">
		<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-ex-collapse">
			<span class="sr-only">Expand the menu</span>
			<span class="icon-bar"></span>
			<span class="icon-bar"></span>
			<span class="icon-bar"></span>
		</button>
	</div>
	<div class="collapse navbar-collapse navbar-ex-collapse">
		<?php
		// @TODO: normalize items & apply friendly urls
		$this->widget( 'zii.widgets.CMenu', [
			'items'          => [
				[ 'label' => 'Home', 'url' => [ 'site/index' ] ],
				[ 'label' => 'About', 'url' => [ 'site/about' ] ],
				[ 'label' => 'Documentation', 'url' => [ 'site/docs' ] ],
				[ 'label' => 'Tutorials', 'url' => [ 'site/help' ] ],
				[ 'label' => 'FAQ', 'url' => [ 'site/faq' ] ],
			],
			'activeCssClass' => 'active',
			'htmlOptions'    => [ 'class' => 'nav navbar-nav' ],
		] );
		?>
	</div>
</nav>

How do you add the search form?