composer require lg-xenos/yii2-multiple-selector
backend/view/test/test.php
echo $form
->field($model, 'main_image')
->widget(\lgxenos\yii2\imgSelector\ImageSelector::className());
->widget(\lgxenos\yii2\multipleSelector\MultipleSelector::className(), ['items' => SomeModel::getDropdownArray(), 'multiple' => 1]);