Fatal error: Uncaught Error: Interface "Kreait\Firebase\Auth\SignIn\Handler" not found in D:\xampp\htdocs\vendor\kreait\firebase-php\src\Firebase\Auth\SignIn\GuzzleHandler.php:38 Stack trace: #0 {main} thrown in D:\xampp\htdocs\vendor\kreait\firebase-php\src\Firebase\Auth\SignIn\GuzzleHandler.php on line 38