Fixes #5452: Errors occurring after the response is sent are not displayed

framework/CHANGELOG.md

@@ -7,6 +7,7 @@ Yii Framework 2 Change Log
 - Bug #4471: `yii\caching\ApcCache::getValues()` now returns array in case of APC is installed but not enabled in CLI mode (samdark, cebe)
 - Bug #4889: Application was getting into redirect loop when user wasn't allowed accessing login page. Now shows 403 (samdark)
 - Bug #5402: Debugger was not loading when there were closures in asset classes (samdark)
+- Bug #5452: Errors occurring after the response is sent are not displayed (qiangxue) 
 - Bug #5570: `yii\bootstrap\Tabs` would throw an exception if `content` is not set for one of its `items` (RomeroMsk)
 - Bug #5584: `yii\rbac\DbRbacManager` should not delete items when deleting a rule on a database not supporting cascade update (mdmunir)
 - Bug #5601: Simple conditions in Query::where() and ActiveQuery::where() did not allow `yii\db\Expression` to be used as the value (cebe, stevekr)

framework/web/ErrorHandler.php

@@ -69,6 +69,7 @@ class ErrorHandler extends \yii\base\ErrorHandler
     {
         if (Yii::$app->has('response')) {
             $response = Yii::$app->getResponse();
+            $response->isSent = false;
         } else {
             $response = new Response();
         }