public function toArray()
    {
        return array(
            'title'    => $this->title,
            'code'     => $this->code,
            'amount'   => $this->amount,
            'price'    => $this->price,
            'vat'      => $this->vat,
            'discount' => $this->discount,
            'type'     => $this->type,
        );
    }