public static function clear($cacheIdPrefix)
    {
        if (!extension_loaded('apc') || PHP_SAPI == 'cli') {
            self::$_cache = array();
            //don't use $cacheIdPrefix as filenames are base64 encoded
            foreach (glob('cache/simpleStatic/*') as $f) {
                unlink($f);
            }
            if (extension_loaded('apc')) {
                Kwf_Util_Apc::callClearCacheByCli(array('clearCacheSimpleStatic'=>$cacheIdPrefix));
            }
        } else {
            if (!class_exists('APCIterator')) {
                throw new Kwf_Exception_NotYetImplemented("We don't want to clear the whole");
            } else {
                static $prefix;
                if (!isset($prefix)) $prefix = Kwf_Cache_Simple::$uniquePrefix.'-';
                $it = new APCIterator('user', '#^'.preg_quote($prefix.$cacheIdPrefix).'#', APC_ITER_NONE);
                if ($it->getTotalCount() && !$it->current()) {
                    //APCIterator is borked, delete everything
                    //see https://bugs.php.net/bug.php?id=59938
                    if (extension_loaded('apcu')) {
                        apc_clear_cache();
                    } else {
                        apc_clear_cache('user');
                    }
                } else {
                    //APCIterator seems to work, use it for deletion
                    apc_delete($it);
                }
            }
        }
    }