Invalid key problem with JWT token and PHP8

Question

Well I’m performing some tests of my project on PHP8 and I’m already refactoring it with some new features of PHP8.

But I’m racking my brain with a library I use to work with JWT token.

In this case the library and this: https://github.com/adhocore/php-jwt

Good use it by informing a key that was generated as follows:

ssh-keygen -t rsa -b 1024 -m PEM -f ws.key

I call the class that:

$jwt = new JWT("/var/www/ws.key", "RS256");

But I’m always making that mistake:

"Invalid key: Should be resource of private key"

Well I went to analyze the library code to verify where the error occurs:

    /**
 * Throw up if key is not resource or file path to private key.
 */
protected function validateKey()
{
    if (\is_string($key = $this->key)) {
        if (\substr($key, 0, 7) !== 'file://') {
            $key = 'file://' . $key;
        }

        $this->key = \openssl_get_privatekey($key, $this->passphrase ?: '');
    }

    if (!\is_resource($this->key)) {
        throw new JWTException('Invalid key: Should be resource of private key', static::ERROR_KEY_INVALID);
    }
}

Well the strange thing is that the same code and key run on a php7.4 server.

Well I’m not getting the bug, Obs I’m running Debian 10 and PHP8.

OBS: If I document the check that’s giving the error:

if (!\is_resource($this->key)) {
        throw new JWTException('Invalid key: Should be resource of private key', static::ERROR_KEY_INVALID);
    }

Everything works fine, which indicates that the key is created correctly. Something in is_resource switched from PHP7.4 to PHP8 and is causing this error. I am unable to identify the fault.