- Добавили отключение буфера и его очистку

common/components/BaseForm.php

@@ -238,7 +238,7 @@ class BaseForm extends \yii\widgets\ActiveForm
         }
         $form->end();
         $out = ob_get_contents();
-        ob_get_clean();
+        ob_end_clean();
         $this->out = $out;
         self::run();
     }

common/modules/school/views/course/index.php

@@ -98,7 +98,7 @@ WidgetAssetBundle::register($this);
 <div class="white-popup-block mfp-hide">
     <?php
     $modelUser = new User();
-//    $formPopup = new \common\components\BaseForm('/common/modules/users/forms/RegistrationUserPopupForm', $modelUser);
+    $formPopup = new \common\components\BaseForm('/common/modules/users/forms/RegistrationUserPopupForm', $modelUser);
 //    \Yii::$app->controller->renderPartial('@common/modules/users/widgets/views/RegistrationWidget', ['formLoginPopup' => $formPopup->out]);
     ?>
     <?php //echo RegistrationWidget::widget(); ?>