JWT encode not working in PHP with Firebase

I am using "firebase/php-jwt": "^6.10" for one my JWT and PHP integration.

// Path to the key file
$key_file = '/var/www/mykey.key';

// Check if the key file exists and read the contents
if (!file_exists($key_file)) {
    die('Key file not found.');
}
$key = file_get_contents($key_file);  /


$kid = // Hex value of directory path

// JWT Payload
$payload = [
    'iss' => 'http://yourdomain.com',  // Issuer
    'aud' => 'http://yourdomain.com',  // Audience
    'iat' => time(),  // Issued at
    'exp' => time() + 3600,  // Expiration (1 hour)
    'data' => [
        'user_id' => $user['id'],
        'email' => $user['email'],
        'role' => $user['role'],
        'is_admin' => $user['isadmin']
    ]
];

// JWT Header with `kid`
$header = [
    'alg' => 'HS256',
    'typ' => 'JWT',
    'kid' => $kid  // Add the `kid` parameter in the header
];

// Encode JWT with header and payload
$jwt = JWT::encode($payload, new Key($key, 'HS256'), $header);

When I execute the code, it seems like the encode function is somehow updated. It throws an error

Uncaught TypeError: Argument 3 passed to FirebaseJWTJWT::encode() must be of the type string, array given, called in /var/www/html/index.php

Basically, on this line

 $jwt = JWT::encode($payload, new Key($key, 'HS256'), $header);

I’m not sure what I’m doing wrong. I want to add the kid parameter in my header that the user can later use for directory traversal.