Yii2 dropdown multiple selected values - yii2

Question

I used Yii2 multiple selection dropdown , it is working fine at create but not showing me selected values on update!
Form:
$form->field($model, 'categories[]')
->dropDownList($model->CategoryDropdown,
[
'multiple'=>'multiple'
'class'=>'chosen-select input-md required',
]
)->label("Add Categories");
Model:
public function getCategoryDropdown()
{
$listCategory = Category::find()->select('ID,name')
->where(['is_subcategory' => 'Yes'])
->andWhere(['status' => 'active','approved' => 'active'])
->all();
$list = ArrayHelper::map( $listCategory,'ID','name');
return $list;
}
Controller:
public function actionCreate(){
...
$model->categories = implode(",",$_POST['Company']['categories']);
...
return $this->render('create', [
'model' => $model,
]);
}
public function actionUpdate($id)
{
$model = $this->findModel($id);
echo $model->categories; // 1,2,4,5 values already assigned
...
return $this->render('update', [
'model' => $model,
]);
}
Database:
1,2,4,5
How I can show multi selected values in dropdown when I update my recored?

Answer 1

all your code is ok just need echo your $form->...
echo $form->field($model, 'categories[]')
->dropDownList($model->CategoryDropdown,
[
'multiple'=>'multiple',
'class'=>'chosen-select input-md required',
]
)->label("Add Categories");
or use <?= ?> in view!

Answer 2

Here is solution:
Form
<?=
$form->field($model, 'categories')
->dropDownList($model->CategoryDropdown,
[
'class'=>'chosen-select input-md required',
'multiple'=>'multiple'
]
)->label("Add Categories");
?>
Controller:
public function actionCreate(){
...
$model->categories = implode(",",$_POST['Company']['categories']);
...
return $this->render('create', [
'model' => $model,
]);
}
public function actionUpdate($id)
{
$model = $this->findModel($id);
$model->categories = explode(',', $model->categories);
...
if($model->load(Yii::$app->request->post()))
{
$model->categories = implode(",",$_POST['Company']['categories']);
...
$model->save()
}
return $this->render('update', [
'model' => $model,
]);
}

Answer 3

I would highly recommend to use Select2 from krajee it has all the options that you might need, using multiple in dropDownList() will make you able to choose multiple values but by pressing and holding Ctrl and choosing which is not comfortable as choosing them using Select2.
They did an amazing job i highly recommend anyone with this problem to use it.
Please check the documentations.
https://demos.krajee.com/widget-details/select2