Jose\Object\JWS::getEncodedPayload PHP Method

    public function getEncodedPayload(SignatureInterface $signature)
    {
        if (true === $this->isPayloadDetached()) {
            return;
        }
        if (null !== $this->encoded_payload) {
            return $this->encoded_payload;
        }
        $payload = $this->getPayload();
        if (!is_string($payload)) {
            $payload = json_encode($payload);
        }
        Assertion::notNull($payload, 'Unsupported payload.');
        return $this->isPayloadEncoded($signature) ? Base64Url::encode($payload) : $payload;
    }