icingaweb2/application/layouts/scripts/parts/navigation.phtml

<?php

// Don't render a menu for unauthenticated users unless menu is auth aware
if (! $this->auth()->isAuthenticated()) {
    return;
}

// Current url
$url = Icinga\Web\Url::fromRequest()->getRelativeUrl();
$menu = Icinga\Web\Menu::fromConfig();

?>
<div id="menu">
  <form action="<?= $this->href('search') ?>" method="post"><input type="text" name="q" class="search" placeholder="Search..." autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false" /></form>
<?= $this->partial('parts/menu.phtml', array(
    'items' => $menu->getChildren(),
    'url'   => $url
))
?>
</div>