/**
  * clear method
  *
  * API DIFFERENCE
  * if a topKey is specified, delete everything under setting-dir/topKey
  *
  * @param bool $check false
  * @return void
  * @access public
  */
 public function clear($topKey = false)
 {
     if (MiCache::$setting === null) {
         MiCache::config();
     }
     if ($topKey) {
         unset(MiCache::$_appSettingCache['_' . $topKey]);
     } else {
         MiCache::$_appSettingCache = array();
     }
     Cache::clear($topKey, MiCache::$setting);
 }