Json key is missing the refresh token field in google photos api

I am creating a app using google photos api in php. Here is my code

function connectWithGooglePhotos()
{
$clientSecretJson = json_decode(
    file_get_contents('credentials.json'),
    true
)['web'];
$clientId = $clientSecretJson['client_id'];
$clientSecret = $clientSecretJson['client_secret'];
$tokenUri = $clientSecretJson['token_uri'];
$redirectUri = $clientSecretJson['redirect_uris'][0];
$scopes = ['https://www.googleapis.com/auth/photoslibrary'];

$oauth2 = new OAuth2([
    'clientId' => $clientId,
    'clientSecret' => $clientSecret,
    'authorizationUri' => 'https://accounts.google.com/o/oauth2/v2/auth',
    'redirectUri' => $redirectUri,
    'tokenCredentialUri' => 'https://www.googleapis.com/oauth2/v4/token',
    'scope' => $scopes,
]);

// The authorization URI will, upon redirecting, return a parameter called code.
if (!isset($_GET['code'])) {
    $authenticationUrl = $oauth2->buildFullAuthorizationUri(['access_type' => 'offline']);
    header('Location: ' . $authenticationUrl);
} else {
    // With the code returned by the OAuth flow, we can retrieve the refresh token.
    $oauth2->setCode($_GET['code']);
    $authToken = $oauth2->fetchAuthToken();
    $refreshToken = $authToken['access_token'];

    // The UserRefreshCredentials will use the refresh token to 'refresh' the credentials when
    // they expire.
    $_SESSION['credentials'] = new UserRefreshCredentials(
        $scopes,
        [
            'client_id' => $clientId,
            'client_secret' => $clientSecret,
            'refreshToken' => $refreshToken,
        ]
    );

    $photosLibraryClient = new PhotosLibraryClient(['credentials' => $_SESSION['credentials']]);
}

return $photosLibraryClient;
}

Here is the error while redirect to authenticate

Fatal error: Uncaught InvalidArgumentException: json key is missing the refresh_token field in C:\xampp\htdocs\gphotos\vendor\google\auth\src\Credentials\UserRefreshCredentials.php:78 Stack trace: #0 C:\xampp\htdocs\gphotos\config.php(49): Google\Auth\Credentials\UserRefreshCredentials->__construct(Array, Array) #1 C:\xampp\htdocs\gphotos\index.php(5): connectWithGooglePhotos() #2 {main} thrown in C:\xampp\htdocs\gphotos\vendor\google\auth\src\Credentials\UserRefreshCredentials.php on line 78

Any solutions will be appreciated !

'refreshToken' needs to be 'refresh_token' because the key for refresh token is refresh_token

so you need to change your credentials to

[
   'client_id' => $clientId,
   'client_secret' => $clientSecret,
   'refresh_token' => $refreshToken,
]