Jose\Verifier::getAlgorithm PHP Method

    private function getAlgorithm(Object\SignatureInterface $signature)
    {
        $complete_headers = array_merge($signature->getProtectedHeaders(), $signature->getHeaders());
        Assertion::keyExists($complete_headers, 'alg', 'No "alg" parameter set in the header.');
        $algorithm = $this->getJWAManager()->getAlgorithm($complete_headers['alg']);
        Assertion::isInstanceOf($algorithm, Algorithm\SignatureAlgorithmInterface::class, sprintf('The algorithm "%s" is not supported or does not implement SignatureInterface.', $complete_headers['alg']));
        return $algorithm;
    }