How to implement validation of one form for two models?

Question

Yii

I have 2 connected models in the form, the first model validates normally, and the second one does not validate at all, and you can save an empty field, which is unacceptable.
Here is the models/client code

class Client extends \yii\db\ActiveRecord
{
    const SCENARIO_DEFAULT = 'default';
    const SCENARIO_CREATE = 'create';
public static function tableName()
    {
        return 'client';
    }

    public function scenarios()
    {
        return [
            self::SCENARIO_DEFAULT => ['id', 'fio', 'phone', 'emaail', 'home','street', 'apartment'],
            self::SCENARIO_CREATE => ['id'],
        ];
    }
public function rules()
    {
        return [
            [['id'], 'required', 'on' => self::SCENARIO_CREATE],
            [['fio', 'phone'], 'required', 'on' => self::SCENARIO_DEFAULT],
            ...
        ];
    }

In models/zakaz model

public function getIdClient()
    {
        return $this->hasOne(Client::className(), ['id' => 'id_client']);
    }

In controllers/ZakazController

public function actionUpdate($id)
    {
        $model = $this->findModel($id);
        $client = new Client();
        $client->scenario = Client::SCENARIO_CREATE;

        if ($model->load(Yii::$app->request->post())) {
            $model->id_client = ArrayHelper::getValue(Yii::$app->request->post('Client'), 'id');
            }
            $model->validate();
            if (!$model->save()) {
                Yii::$app->session->addFlash('errors', 'Произошла ошибка');
                print_r($model->getErrors());
            } else {
                $model->save();
                Yii::$app->session->addFlash('update', 'Успешно отредактирован заказ');
            }
        }

        return $this->render('update', [
            'model' => $model,
            'client' => $client,
        ]);
    }

And in the views/update view

<div class="col-xs-12">
<?= $form->field($model, 'name')->textInput(['placeholder' => 'Имя клиента', 'class' => 'inputForm'])->label(false) ?>
            <?php !$model->isNewRecord ? $client->id = $model->id_client : null ?>
            <?php if (Yii::$app->request->get('phone')) {
                echo $form->field($client, 'id')->widget(Select2::className(), [
                    'data' => [Yii::$app->request->get('phone')],
                    'disabled' => true,
                ])->label(false);
            } else {
                echo $form->field($client, 'id')->widget(Select2::className(), [
                    'data' => ArrayHelper::map(Client::find()->all(), 'id', 'phone', 'fio'),
                    'options' => ['placeholder' => 'Введите номер телефона'],
                ])->label(false);
            }?>
        </div>

Answer 1

There is no saving at all in your controller $client. No save - no validation.
Here is the documentation for working with multiple models:
www.yiiframework.com/doc-2.0/guide-input-multiple-...