/* @var $courses appmodelsCourse[] */

function items($my_courses)
{
    $items = [];
    foreach ($my_courses as $course) {
        array_push($items, ['label' => $course->title, 'url' =>
        Url::to(['course', 'id' => $course->id])]);
    }
    return $items;
}

$menuItems = [
// other items ...
    'label' => 'Courses', 'items' => items($courses)
];

echo Nav::widget([
    'options' => ['class' => 'uk-navbar-item'],
    'encodeLabels' => false,
    'items' => $menuItems
 ]);