echo Select2::widget([
'name' => 'my-select2',
'data' => [1 => 'One', 2 => 'Two'],
'options' => [
'placeholder' => 'Select a number ...',
'options' => [
2 => ['disabled' => true],
]
],
]);
<select>
<option value="1">One</option>
<option value="2" disabled="disabled">Two</option>
</select>