Jose\Object\JWKSetPEM::getPEM PHP Method

    private function getPEM(JWKInterface $key)
    {
        switch ($key->get('kty')) {
            case 'RSA':
                return (new RSAKey($key))->toPEM();
            case 'EC':
                return (new ECKey($key))->toPEM();
            default:
                throw new \InvalidArgumentException('Unsupported key type.');
        }
    }