Contao\Message::hasMessages PHP Method

    public static function hasMessages($strScope = TL_MODE)
    {
        return static::hasError($strScope) || static::hasConfirmation($strScope) || static::hasNew($strScope) || static::hasInfo($strScope) || static::hasRaw($strScope);
    }

 /**
  * Add the template output to the cache and add the cache headers
  */
 protected function addToCache()
 {
     /** @var PageModel $objPage */
     global $objPage;
     $intCache = 0;
     // Decide whether the page shall be cached
     if (!isset($_GET['file']) && !isset($_GET['token']) && empty($_POST) && !BE_USER_LOGGED_IN && !FE_USER_LOGGED_IN && !$_SESSION['DISABLE_CACHE'] && !isset($_SESSION['LOGIN_ERROR']) && !\Message::hasMessages() && intval($objPage->cache) > 0 && !$objPage->protected) {
         $intCache = time() + intval($objPage->cache);
     }
     // Server-side cache
     if ($intCache > 0 && (\Config::get('cacheMode') == 'both' || \Config::get('cacheMode') == 'server')) {
         // If the request string is empty, use a special cache tag which considers the page language
         if (\Environment::get('relativeRequest') == '') {
             $strCacheKey = \Environment::get('host') . '/empty.' . $objPage->language;
         } else {
             $strCacheKey = \Environment::get('host') . '/' . \Environment::get('relativeRequest');
         }
         // HOOK: add custom logic
         if (isset($GLOBALS['TL_HOOKS']['getCacheKey']) && is_array($GLOBALS['TL_HOOKS']['getCacheKey'])) {
             foreach ($GLOBALS['TL_HOOKS']['getCacheKey'] as $callback) {
                 $this->import($callback[0]);
                 $strCacheKey = $this->{$callback[0]}->{$callback[1]}($strCacheKey);
             }
         }
         // Add a suffix if there is a mobile layout (see #7826)
         if ($objPage->mobileLayout > 0) {
             if (\Input::cookie('TL_VIEW') == 'mobile' || \Environment::get('agent')->mobile && \Input::cookie('TL_VIEW') != 'desktop') {
                 $strCacheKey .= '.mobile';
             } else {
                 $strCacheKey .= '.desktop';
             }
         }
         // Replace insert tags for caching
         $strBuffer = $this->replaceInsertTags($this->strBuffer);
         $strBuffer = $this->replaceDynamicScriptTags($strBuffer);
         // see #4203
         // Add the cache file header
         $strHeader = sprintf("<?php /* %s */ \$expire = %d; \$content = %s; \$type = %s; \$files = %s; \$assets = %s; ?>\n", $strCacheKey, (int) $intCache, var_export($this->strContentType, true), var_export($objPage->type, true), var_export(TL_FILES_URL, true), var_export(TL_ASSETS_URL, true));
         $strCachePath = str_replace(TL_ROOT . '/', '', \System::getContainer()->getParameter('kernel.cache_dir'));
         // Create the cache file
         $strMd5CacheKey = md5($strCacheKey);
         $objFile = new \File($strCachePath . '/contao/html/' . substr($strMd5CacheKey, 0, 1) . '/' . $strMd5CacheKey . '.html');
         $objFile->write($strHeader);
         $objFile->append($this->minifyHtml($strBuffer), '');
         $objFile->close();
     }
     // Client-side cache
     if (!headers_sent()) {
         if ($intCache > 0 && (\Config::get('cacheMode') == 'both' || \Config::get('cacheMode') == 'browser')) {
             header('Cache-Control: private, max-age=' . ($intCache - time()));
             header('Last-Modified: ' . gmdate('D, d M Y H:i:s', time()) . ' GMT');
             header('Expires: ' . gmdate('D, d M Y H:i:s', $intCache) . ' GMT');
         } else {
             header('Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0');
             header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT');
             header('Expires: Fri, 06 Jun 1975 15:10:00 GMT');
         }
     }
 }