think\cache\driver\Memcached::dec PHP Method

    public function dec($name, $step = 1)
    {
        $key = $this->getCacheKey($name);
        $value = $this->handler->get($key) - $step;
        $res = $this->handler->set($key, $value);
        if (!$res) {
            return false;
        } else {
            return $value;
        }
    }