How to organize multiselect dropdownlist using kartik-select2 extension - php

Question

I need to organize multiselect dropdownlist. I tried like this:
<?= $form->field($model, 'receiver_id')->widget(Select2::classname(),
[ 'data' => ArrayHelper::map(User::find()->all(),'id','username'),
'options' =>
['placeholder' => 'Select receivers...', 'multiple' => true],
'pluginOptions' =>
[ 'tags' => true,
'maximumInputLength' => 10
],
]);
?>
In the view it seems correctly, in the textfield receivers appear one by one, but when I press "Send" button it says that Receiver ID must be an integer. How can I solve this issue? I need to duplicate one db record for different receivers which I select using select2 dropdown list. For example, I choose in dropdownlist user1 and user2, "Send" action should work twice accordingly. In the db table named as 'letter' should be two same records with different id and receiver_id.
My actionCreate function in the Controller class:
public function actionCreate()
{
$model = new Letter();
if ($model->load(Yii::$app->request->post())) {
foreach($model->receiver_id as $r_id){
$save = new Letter();
$save->type_id = $model->type_id;
$save->subject = $model->subject;
$save->body = $model->body;
$save->sender_id = $model->sender_id;
$save->start_date = $model->start_date;
$save->end_date = $model->end_date;
$save->receiver_id = $r_id;
$save->save();
}
$model->attachment = UploadedFile::getInstance($model, 'attachment');
$filename = pathinfo($model->attachment , PATHINFO_FILENAME);
$ext = pathinfo($model->attachment , PATHINFO_EXTENSION);
$newFname = $filename.'.'.$ext;
$path=Yii::getAlias('#webroot').'/uploads/';
if(!empty($newFname)){
$model->attachment->saveAs($path.$newFname);
$model->attachment = $newFname;
if($model->save()){
return $this->redirect(['view', 'id' => $model->id]);
}
}
}
return $this->render('create', [
'model' => $model,
]);
}
My IDE says on "$model->receiver_id" that "Expected types array or object, Actual: int"
Thanks in advance.

Answer 1

do receiver_id as array on your model; and
foreach($model->receiver_id as $r_id){
$save = new YourModel();
$save->yourProperty = $model->yourProperty;
....
$save->receiver_id = $r_id;
$save->save();
}