public function del($fd, $flag)
    {
        switch ($flag) {
            case EventInterface::EV_READ:
                return $this->removeReadStream($fd);
            case EventInterface::EV_WRITE:
                return $this->removeWriteStream($fd);
            case EventInterface::EV_SIGNAL:
                return $this->removeSignal($fd);
            case EventInterface::EV_TIMER:
            case EventInterface::EV_TIMER_ONCE;
                if (isset($this->_timerIdMap[$fd])){
                    $timer_obj = $this->_timerIdMap[$fd];
                    unset($this->_timerIdMap[$fd]);
                    $this->cancelTimer($timer_obj);
                    return true;
                }
        }
        return false;
    }