Pimcore\Cache::removeIgnoredTagOnClear PHP Method

    public static function removeIgnoredTagOnClear($tag)
    {
        $tagPosition = array_search($tag, self::$ignoredTagsOnClear);
        if ($tagPosition !== false) {
            array_splice(self::$ignoredTagsOnClear, $tagPosition, 1);
        }
    }

 public function clearOutputCacheAction()
 {
     $this->checkPermission("clear_cache");
     // remove "output" out of the ignored tags, if a cache lifetime is specified
     Cache::removeIgnoredTagOnClear("output");
     // empty document cache
     Cache::clearTag("output");
     $this->_helper->json(array("success" => true));
 }