Fatal error: Uncaught Error: Class "GuzzleHttp\Promise\Tests\Thennable" not found in C:\Users\Administrator\Desktop\xamp\htdocs\sdk\guzzlehttp\promises\tests\NotPromiseInstance.php:10 Stack trace: #0 {main} thrown in C:\Users\Administrator\Desktop\xamp\htdocs\sdk\guzzlehttp\promises\tests\NotPromiseInstance.php on line 10