Fixes #3979: Alert widget in advanced app is now able to display multiple flash…

apps/advanced/frontend/widgets/Alert.php

@@ -11,9 +11,17 @@ namespace frontend\widgets;
  * Alert widget renders a message from session flash. All flash messages are displayed
  * in the sequence they were assigned using setFlash. You can set message as following:
  *
- * - \Yii::$app->getSession()->setFlash('error', 'This is the message');
- * - \Yii::$app->getSession()->setFlash('success', 'This is the message');
- * - \Yii::$app->getSession()->setFlash('info', 'This is the message');
+ * ```php
+ * \Yii::$app->getSession()->setFlash('error', 'This is the message');
+ * \Yii::$app->getSession()->setFlash('success', 'This is the message');
+ * \Yii::$app->getSession()->setFlash('info', 'This is the message');
+ * ```
+ *
+ * Multiple messages could be set as follows:
+ *
+ * ```php
+ * \Yii::$app->getSession()->setFlash('error', ['Error 1', 'Error 2']);
+ * ```
  *
  * @author Kartik Visweswaran <kartikv2@gmail.com>
  * @author Alexander Makarov <sam@rmcreative.ru>
@@ -47,8 +55,10 @@ class Alert extends \yii\bootstrap\Widget
         $flashes = $session->getAllFlashes();
         $appendCss = isset($this->options['class']) ? ' ' . $this->options['class'] : '';
 
-        foreach ($flashes as $type => $message) {
+        foreach ($flashes as $type => $data) {
             if (isset($this->alertTypes[$type])) {
+                $data = (array) $data;
+                foreach ($data as $message) {
                     /* initialize css class for each alert box */
                     $this->options['class'] = $this->alertTypes[$type] . $appendCss;
 
@@ -60,6 +70,7 @@ class Alert extends \yii\bootstrap\Widget
                         'closeButton' => $this->closeButton,
                         'options' => $this->options,
                     ]);
+                }
 
                 $session->removeFlash($type);
             }