Kartik Select2 return null - php

Question

i have a problem with Kartik Select2. When I want save multiple data in my controller, nothing is saved. And I remove foreach in controller, Yii return me error with information about $university_id IS NULL.
User Form
<?= $form->field($user_university, 'university_id')->widget(Select2::classname(),[
'name' => 'university_id[]',
'data' => ArrayHelper::map(
\app\models\University::find()->asArray()->all(),
'id',
function ($university) {
return $university['name'];
}
),
'size' => Select2::MEDIUM,
'options' => ['placeholder' => 'Select a state ...', 'multiple' => true],
'pluginOptions' => [
'allowClear' => true
],
]); ?>
User Controller
$user = new User();
$user->scenario = User::SCENARIO_CREATE;
$auth_assignment = new AuthAssignment();
$user_company = new UserCompany();
$user_university = new UserUniversity();
$user_status = UserStatus::find()
->select('id')
->where(['name' => UserStatus::NON_AUTHORIZED_USER])
->one();
if ($user->load(Yii::$app->request->post()) && $auth_assignment->load(Yii::$app->request->post())) {
$user->auth_key = Yii::$app->getSecurity()->generateRandomString();
$user->password_hash = Yii::$app->getSecurity()->generatePasswordHash($user->password);
$user->password_reset_token = Yii::$app->getSecurity()->generateRandomString();
$user->status_id = $user_status->id;
$user->created_at = date('Y-m-d H:i:s');
$user->updated_at = date('Y-m-d H:i:s');
if ($user->save()) {
$auth_assignment->user_id = $user->id;
$auth_assignment->created_at = date('Y-m-d H:i:s');
$universities = $user_university->university_id;
foreach((array) $universities as $university)
{
$newUserUniversity = new UserUniversity();
$newUserUniversity->user_id = $user->id;
$newUserUniversity->university_id = $university;
$newUserUniversity->created_at = date('Y-m-d H:i:s');
$newUserUniversity->save(false);
}...
User University Model Rule
public function rules()
{
return [
[['user_id', 'university_id', 'created_at'], 'required'],
[['user_id', 'university_id','confirm'], 'integer'],
[['created_at','university_id'], 'safe'],
[['university_id'], 'exist', 'skipOnError' => true, 'targetClass' => University::className(), 'targetAttribute' => ['university_id' => 'id']],
[['user_id'], 'exist', 'skipOnError' => true, 'targetClass' => User::className(), 'targetAttribute' => ['user_id' => 'id']],
];
}

Answer 1

Looking at your code i can't see where you are loading the data from the post request into the $user_university before you start looping on the university_id. You need to call $user_university->load(Yii::$app->request->post()), look the following piece of code from your script
if ($user->save()) {
$auth_assignment->user_id = $user->id;
$auth_assignment->created_at = date('Y-m-d H:i:s');
// this below line will give you an empty string rather than
// the selected ids of the `university` that you selected
// in the multi-dropdown
$universities = $user_university->university_id;
and the very next line is the foreach((array) $universities as $university) in which you are trying to save which won't run even once, as there isnt any array loaded in the $unversities. So you can add a call before you get the array from the attribute, dont know if your requirements are to return the user with an error if the data is not loaded for the $user_university otherwise you need to add it to the main check
if ($user->load(Yii::$app->request->post()) && $auth_assignment->load(Yii::$app->request->post()) &&
$user->university->load(Yii::$app->request->post())) {
So your code should look like below
$user = new User();
$user->scenario = User::SCENARIO_CREATE;
$auth_assignment = new AuthAssignment();
$user_company = new UserCompany();
$user_university = new UserUniversity();
$user_status = UserStatus::find()
->select('id')
->where(['name' => UserStatus::NON_AUTHORIZED_USER])
->one();
//validate all models
$allModelsValid=$user->load(Yii::$app->request->post()) && $auth_assignment->load(Yii::$app->request->post()) && $user_university->load(Yii::$app->request->post());
if ($allModelsValid) {
$user->auth_key = Yii::$app->getSecurity()->generateRandomString();
$user->password_hash = Yii::$app->getSecurity()->generatePasswordHash($user->password);
$user->password_reset_token = Yii::$app->getSecurity()->generateRandomString();
$user->status_id = $user_status->id;
$user->created_at = date('Y-m-d H:i:s');
$user->updated_at = date('Y-m-d H:i:s');
if ($user->save()) {
$auth_assignment->user_id = $user->id;
$auth_assignment->created_at = date('Y-m-d H:i:s');
$universities = $user_university->university_id;
foreach((array) $universities as $university)
{
$newUserUniversity = new UserUniversity();
$newUserUniversity->user_id = $user->id;
$newUserUniversity->university_id = $university;
$newUserUniversity->created_at = date('Y-m-d H:i:s');
$newUserUniversity->save(false);
}...
Also apart from above i dont find a reason to use the name as university_id[] for the dropdown rather than university_id

Answer 2

There are multiple ways of Usage of select2 now currently you are using Usage with ActiveForm and model see below multiple ways.
use kartik\select2\Select2
// Usage with ActiveForm and model
echo $form->field($model, 'state_1')->widget(Select2::classname(), [
'data' => $data,
'options' => ['placeholder' => 'Select a state ...'],
'pluginOptions' => [
'allowClear' => true
],
]);
// With a model and without ActiveForm
echo Select2::widget([
'model' => $model,
'attribute' => 'state_2',
'data' => $data,
'options' => ['placeholder' => 'Select a state ...'],
'pluginOptions' => [
'allowClear' => true
],
]);
// Without model and implementing a multiple select
echo '<label class="control-label">Provinces</label>';
echo Select2::widget([
'name' => 'state_10',
'data' => $data,
'options' => [
'placeholder' => 'Select provinces ...',
'multiple' => true
],
]);
// A disabled select2 list input
echo '<label class="control-label">State</label>';
echo Select2::widget([
'name' => 'state_11',
'data' => $data,
'disabled' => true
]);
I guess your problem is in :
'data' => ArrayHelper::map(
\app\models\University::find()->asArray()->all(),
'id',
function ($university) {
return $university['name'];
}
),
Please check data attribute .. check you are passing correct array or not.