Jose\Behaviour\EncrypterTrait::getCompressionMethod PHP Method

    private function getCompressionMethod(Object\JWEInterface $jwe)
    {
        $method = null;
        $nb_recipients = $jwe->countRecipients();
        for ($i = 0; $i < $nb_recipients; $i++) {
            $complete_headers = array_merge($jwe->getSharedProtectedHeaders(), $jwe->getSharedHeaders(), $jwe->getRecipient($i)->getHeaders());
            if (array_key_exists('zip', $complete_headers)) {
                if (null === $method) {
                    if (0 === $i) {
                        $method = $complete_headers['zip'];
                    } else {
                        throw new \InvalidArgumentException('Inconsistent "zip" parameter.');
                    }
                } else {
                    Assertion::eq($method, $complete_headers['zip'], 'Inconsistent "zip" parameter.');
                }
            } else {
                Assertion::eq(null, $method, 'Inconsistent "zip" parameter.');
            }
        }
        if (null === $method) {
            return;
        }
        $compression_method = $this->getCompressionManager()->getCompressionAlgorithm($method);
        Assertion::isInstanceOf($compression_method, Compression\CompressionInterface::class, sprintf('Compression method "%s" not supported.', $method));
        return $compression_method;
    }