protected function memcachedGetMulti($keys, $flags)
    {
        if ($this->newGetMultiSignature === null) {
            $this->newGetMultiSignature = (new ReflectionMethod('Memcached', 'getMulti'))->getNumberOfParameters() === 2;
        }
        if ($this->newGetMultiSignature) {
            return $this->memcached->getMulti($keys, $flags);
        } else {
            $null = null;
            return $this->memcached->getMulti($keys, $null, $flags);
        }
    }