code: public function isTemplateFresh($name, $time)
      {
          if (0 === $this->lastModifiedExtension) {
              foreach ($this->extensions as $extension) {
                  $r = new ReflectionObject($extension);
                  if (file_exists($r->getFileName()) && ($extensionTime = filemtime($r->getFileName())) > $this->lastModifiedExtension) {
                      $this->lastModifiedExtension = $extensionTime;
                  }
              }
          }
  
          return $this->lastModifiedExtension <= $time && $this->getLoader()->isFresh($name, $time);
      }
docs: Returns true if the template is still fresh.
  
  Besides checking the loader for freshness information,
  this method also checks if the enabled extensions have
  not changed.
  
  @param string $name The template name
  @param int    $time The last modification time of the cached template
  
  @return bool true if the template is fresh, false otherwise