private function notifyPolls(array $selected, array & $watchers): void
    {
        foreach ($selected as $k => $stream) {
            $k = $k ?: (int) $stream;
            
            if (isset($watchers[$k])) {
                foreach ($watchers[$k] as $watcher) {
                    if (isset($watchers[$k][$watcher->id])) {
                        ($watcher->callback)($watcher->id, $stream);
                    }
                }
            }
        }
    }