update Exception

Author: codercat

README.md

@@ -40,14 +40,14 @@ echo $convertedJwk;
 The PEM for this jwk:
 
 ```
------BEGIN PUBLIC KEY-----\n
-MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvdv73smpkrTIBSM8ka+p\n
-VXbNi7zYalm0R6WFBH4X8PQj8C7VfdckGsA6bTBseOVCTbu187/63yU2U7vqYiqw\n
-SLmkrBVAJjYMJY/XXfncxwqDWR/aa7eIJSKh22H/6yz6kFyF1h/ZSk68CPAEQpvd\n
-9VFAr4VLEwD32Ag6MwymSOxmFWJyddEtttdGcXLSrHcya3RWyG5KAW3Ti+HgNC+x\n
-o/C5LgEsUgjeUq+rc8NBXZrNCY+LJ/R+qtB/+5NkwlMJ/fUMBDcmZuciNOH71q7x\n
-yn0FGmGjrJXnyVJwyDiTrKRO36piMuiaJE2nIRJaLvhDN5M1K2VhSKPuaqUPyxLz\n
-BwIDAQAB\n
------END PUBLIC KEY-----\n
+-----BEGIN PUBLIC KEY-----\r\n
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvdv73smpkrTIBSM8ka+p\r\n
+VXbNi7zYalm0R6WFBH4X8PQj8C7VfdckGsA6bTBseOVCTbu187/63yU2U7vqYiqw\r\n
+SLmkrBVAJjYMJY/XXfncxwqDWR/aa7eIJSKh22H/6yz6kFyF1h/ZSk68CPAEQpvd\r\n
+9VFAr4VLEwD32Ag6MwymSOxmFWJyddEtttdGcXLSrHcya3RWyG5KAW3Ti+HgNC+x\r\n
+o/C5LgEsUgjeUq+rc8NBXZrNCY+LJ/R+qtB/+5NkwlMJ/fUMBDcmZuciNOH71q7x\r\n
+yn0FGmGjrJXnyVJwyDiTrKRO36piMuiaJE2nIRJaLvhDN5M1K2VhSKPuaqUPyxLz\r\n
+BwIDAQAB\r\n
+-----END PUBLIC KEY-----
 ```
 

src/JWKConverter.php

@@ -35,6 +35,10 @@ public function toPEM(array $jwk): string
             throw new JWKConverterException('RSA key type is currently only supported.');
         }
 
+        if (array_key_exists('d', $jwk)) {
+            throw new JWKConverterException('Public key is currently only supported.');
+        }
+
         $rsa = new RSA();
         $base64UrlDecoder = new Base64UrlDecoder();
         $rsa->loadKey(