public function save()
    {
        $this->modifiedTime = new \DateTime('now');

        self::set(
            $this->namespace, 
            base64_encode(serialize($this->instance)), 
            $this->modifiedTime->getTimestamp() + $this->lifetime, 
            $this->path, 
            $this->domain, 
            $this->secure
        );

        return $this;
    }