Config Cross-subdomain authentication

common/config/main.php

@@ -13,6 +13,7 @@ return [
             ]
         ],
         'session' => [
+            'class' => 'yii\web\Session',
             'cookieParams' => [
                 'domain' => '.'.Yii::getAlias('@domainName'),
                 'httpOnly' => true,