Jose\Object\JWKInterface::get PHP Method

    public function get($key);

 /**
  * {@inheritdoc}
  */
 public function getCEK(JWKInterface $key, array $header)
 {
     if (!$key->has('kty') || 'dir' !== $key->get('kty') || !$key->has('dir')) {
         throw new \InvalidArgumentException('The key is not valid');
     }
     return Base64Url::decode($key->get('dir'));
 }