private static function getKeyMaterialAndAlgorithm($keyOrKeyArray, $kid = null)
    {
        if (
            is_string($keyOrKeyArray)
            || is_resource($keyOrKeyArray)
            || $keyOrKeyArray instanceof OpenSSLAsymmetricKey
        ) {
            return array($keyOrKeyArray, null);
        }
        if ($keyOrKeyArray instanceof Key) {
            return array($keyOrKeyArray->getKeyMaterial(), $keyOrKeyArray->getAlgorithm());
        }
        if (is_array($keyOrKeyArray) || $keyOrKeyArray instanceof ArrayAccess) {
            if (!isset($kid)) {
                throw new UnexpectedValueException('"kid" empty, unable to lookup correct key');
            }
            if (!isset($keyOrKeyArray[$kid])) {
                throw new UnexpectedValueException('"kid" invalid, unable to lookup correct key');
            }
            $key = $keyOrKeyArray[$kid];
            if ($key instanceof Key) {
                return array($key->getKeyMaterial(), $key->getAlgorithm());
            }
            return array($key, null);
        }
        throw new UnexpectedValueException(
            '$keyOrKeyArray must be a string|resource key, an array of string|resource keys, '
            . 'an instance of Firebase\JWT\Key key or an array of Firebase\JWT\Key keys'
        );
    }