Dropdown with tree or list of checkboxes. This is extension for Yii2 framework.
<?php
echo \insperedia\treedropdown\DropdownTreeWidget::widget(
[
'data' => [
'item1' => [
'subitem1',
'subitem2',
],
'item2' => [
'subitem3',
'subitem4',
],
]
]
);
?>