diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index b29456ce12..8dc16b6761 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -205,7 +205,7 @@ Yii Framework 2 Change Log
 	- Renamed `yii\web\User::authTimeoutVar` to `authTimeoutParam`
 	- Renamed `yii\web\User::returnUrlVar` to `returnUrlParam`
 - Chg: Added `View::viewFile` and removed `ViewEvent::viewFile` (qiangxue)
-
+- Chg: Changed `Controller::afterAction()`, `Module::afterAction()` and `ActionFilter::afterAction()` to pass `$result` by value instead of reference (qiangxue)
 - New #66: [Auth client library](https://github.com/yiisoft/yii2-authclient) OpenId, OAuth1, OAuth2 clients (klimov-paul)
 - New #706: Added `yii\widgets\Pjax` and enhanced `GridView` to work with `Pjax` to support AJAX-update (qiangxue)
 - New #1393: [Codeception testing framework integration](https://github.com/yiisoft/yii2-codeception) (Ragazzo)
diff --git a/framework/base/ActionFilter.php b/framework/base/ActionFilter.php
index 3b8f8ebd91..6fb114ca03 100644
--- a/framework/base/ActionFilter.php
+++ b/framework/base/ActionFilter.php
@@ -65,7 +65,7 @@ class ActionFilter extends Behavior
 	public function afterFilter($event)
 	{
 		if ($this->isActive($event->action)) {
-			$this->afterAction($event->action, $event->result);
+			$event->result = $this->afterAction($event->action, $event->result);
 		}
 	}
 
@@ -85,9 +85,11 @@ class ActionFilter extends Behavior
 	 * You may override this method to do some postprocessing for the action.
 	 * @param Action $action the action just executed.
 	 * @param mixed $result the action execution result
+	 * @return mixed the processed action result.
 	 */
-	public function afterAction($action, &$result)
+	public function afterAction($action, $result)
 	{
+		return $result;
 	}
 
 	/**
diff --git a/framework/base/Controller.php b/framework/base/Controller.php
index 333c99a2ae..27d234512b 100644
--- a/framework/base/Controller.php
+++ b/framework/base/Controller.php
@@ -126,11 +126,12 @@ class Controller extends Component implements ViewContextInterface
 			Yii::$app->trigger(Application::EVENT_BEFORE_ACTION, $event);
 			if ($event->isValid && $this->module->beforeAction($action) && $this->beforeAction($action)) {
 				$result = $action->runWithParams($params);
-				$this->afterAction($action, $result);
-				$this->module->afterAction($action, $result);
+				$result = $this->afterAction($action, $result);
+				$result = $this->module->afterAction($action, $result);
 				$event = new ActionEvent($action);
-				$event->result = &$result;
+				$event->result = $result;
 				Yii::$app->trigger(Application::EVENT_AFTER_ACTION, $event);
+				$result = $event->result;
 			}
 			$this->action = $oldAction;
 			return $result;
@@ -222,14 +223,17 @@ class Controller extends Component implements ViewContextInterface
 	 * This method is invoked right after an action is executed.
 	 * You may override this method to do some postprocessing for the action.
 	 * If you override this method, please make sure you call the parent implementation first.
+	 * Also make sure you return the action result, whether it is processed or not.
 	 * @param Action $action the action just executed.
 	 * @param mixed $result the action return result.
+	 * @return mixed the processed action result.
 	 */
-	public function afterAction($action, &$result)
+	public function afterAction($action, $result)
 	{
 		$event = new ActionEvent($action);
-		$event->result = &$result;
+		$event->result = $result;
 		$this->trigger(self::EVENT_AFTER_ACTION, $event);
+		return $event->result;
 	}
 
 	/**
diff --git a/framework/base/Module.php b/framework/base/Module.php
index b65ad8b5d1..c82716fb98 100644
--- a/framework/base/Module.php
+++ b/framework/base/Module.php
@@ -658,10 +658,13 @@ class Module extends Component
 	 * This method is invoked right after an action of this module has been executed.
 	 * You may override this method to do some postprocessing for the action.
 	 * Make sure you call the parent implementation so that the relevant event is triggered.
+	 * Also make sure you return the action result, whether it is processed or not.
 	 * @param Action $action the action just executed.
 	 * @param mixed $result the action return result.
+	 * @return mixed the processed action result.
 	 */
-	public function afterAction($action, &$result)
+	public function afterAction($action, $result)
 	{
+		return $result;
 	}
 }
diff --git a/framework/web/PageCache.php b/framework/web/PageCache.php
index 4c8cc508c4..08857d530b 100644
--- a/framework/web/PageCache.php
+++ b/framework/web/PageCache.php
@@ -136,15 +136,12 @@ class PageCache extends ActionFilter
 	}
 
 	/**
-	 * This method is invoked right after an action is executed.
-	 * You may override this method to do some postprocessing for the action.
-	 * @param Action $action the action just executed.
-	 * @param mixed $result the action execution result
+	 * @inheritdoc
 	 */
-	public function afterAction($action, &$result)
+	public function afterAction($action, $result)
 	{
 		echo $result;
 		$this->view->endCache();
-		$result = ob_get_clean();
+		return ob_get_clean();
 	}
 }