private function getHeaderPath($key)
    {
        $parts = explode('/', $key, 2);
        if (count($parts) >= 2) {
            list($extId, $configId) = $parts;
            $ext = common_ext_ExtensionsManager::singleton()->getExtensionById($extId);
            return $ext->getDir().'config/header/'.$configId.'.conf.php';
        } else {
            return null;
        }
    }