Fixes #8613: FragmentCache storing empty content causes problem with PageCache

framework/CHANGELOG.md

@@ -29,6 +29,7 @@ Yii Framework 2 Change Log
 - Enh #8486: Added support to automatically set the `maxlength` attribute for `Html::activeTextArea()` and `Html::activePassword()` (klimov-paul)
 - Enh #8566: Added support for 'only' and 'except' options for `yii\web\AssetManager::publish()` (klimov-paul)
 - Enh #8574: Added `yii\console\controllers\MessageController` support .pot file creation (pgaultier)
+- Enh #8613: `yii\widgets\FragmentCache` will not store empty content anymore which fixes some problems related to `yii\filters\PageCache` (kidol)
 - Chg #6354: `ErrorHandler::logException()` will now log the whole exception object instead of only its string representation (cebe)
 - Chg #8556: Extracted `yii\web\User::getAuthManager()` method (samdark)
 

framework/widgets/FragmentCache.php

@@ -104,6 +104,9 @@ class FragmentCache extends Widget
             echo $content;
         } elseif ($this->cache instanceof Cache) {
             $content = ob_get_clean();
+            if ($content === false || $content === '') {
+                return;
+            }
             array_pop($this->getView()->cacheStack);
             if (is_array($this->dependency)) {
                 $this->dependency = Yii::createObject($this->dependency);