default selected in multiselect dropdown in yii

Question

it will not display default selected value in my multi select dropdown list and i am not getting the mistak. is dropdown list accept array for defalt select array list

public function actionCreate()
{
    .......
        $cust= implode('_',$_POST['supplier'] ['manufacture']);
        $model->customer = $cust;
        $model->save();
    ........
}
public function actionUpdate($id)
{
    $model = $this->findModel($id);
    $model->customer  = explode('_',$model->customer);
    if ($model->load(Yii::$app->request->post())) {
      $cust= implode(',',$_POST['supplier']['manufacturer']);
        $model->customer = $cust`enter code here`;
        $model->save();
        return $this->redirect(['view', 'id' => $model->ID]);
    } else {
        return $this->render('update', [
            'model' => $model,
        ]);
    }
}

View

<?= 
$form->field($model, 'car_manufacturer[]')->dropDownList($model->getcustinfo(), [
    'multiple'=>'multiple',
    'class'=>'chosen-select input-md required',
    ]);
?>

Answer 1

You should use only attribute name.

<?= $form->field($model, 'car_manufacturer')->dropDownList($model->getcustinfo(), [
          'multiple'=>'multiple',
          'class'=>'chosen-select input-md required',  ])?>