<?php $form = ActiveForm::begin([
'id' => 'form-id',
'enableAjaxValidation' => true,
]
); ?>

if ($model->load(Yii::$app->request->post())) {
Yii::$app->response->format = yii\web\Response::FORMAT_JSON;
if ($errors = \yii\widgets\ActiveForm::validate($model)) {
return $errors;
} else {
if($model->save(false)) {
return $this->redirect(['index']); 
}
}
}
return $this->render('create', [
'model' => $model,
]);

if ($model->load(Yii::$app->request->post())) {
if ($model->save()) { 
if (Yii::$app->request->isAjax) {
Yii::$app->response->format = \yii\web\Response::FORMAT_JSON;
return ['success' => true];
}
return $this->redirect(['index']);
} else {
if (Yii::$app->request->isAjax) {
Yii::$app->response->format = \yii\web\Response::FORMAT_JSON;
return \yii\widgets\ActiveForm::validate($model);
}
}
}
if (Yii::$app->request->isAjax) {
return $this->renderAjax('create', [
'model' => $model,
]);
} else {
return $this->render('create', [
'model' => $model,
]);
}