Firebase JWT library can't verify Python JWT token

Question

So I have a client in python and a backend in PHP. The python client is using pyjwt and the php server is using Firebase JWT.

When encoding and decoding tokens within php everything works fine. But when I encode tokens from python and decode them with php the Firebase library returns an error:

Firebase\JWT\SignatureInvalidException Object
(
    [message:protected] => Signature verification failed
    [string:Exception:private] => 
    [code:protected] => 0
    [file:protected] => /var/www/vendor/firebase/php-jwt/src/JWT.php
    [line:protected] => 110
    ...

The encoding python code is the following

import jwt
...
payload = {'sub': self.client.id, 'exp': (datetime.now() + timedelta(days=1)).timestamp()}
context['token'] = jwt.encode(payload, os.environ['JWT_KEY'], algorithm='HS256')

and the PHP code is the following

$key = getenv("JWT_KEY");
return (array) \Firebase\JWT\JWT::decode($token, $key, array('HS256'));

Answer 1

OK, I found the problem. The issue was the secret KEY ussed by the different parties. The key had a problem when trying to be readed by PHP and thats why it was creating different tokens. The libraries are ok, they can communicate between each other without any problem.