找不到php编写器项目类

https://github.com/stevenmaguire/oauth2-microsoft

目前的代码如下所示:

use \Stevenmaguire\OAuth2\Client\Provider\Microsoft;

$provider = new Microsoft([
    // Required
    'clientId'                  => '',
    'clientSecret'              => '',
    'redirectUri'               => 'http://localhost/microsoftToDo/app/microsoft.php',
    // Optional
    'urlAuthorize'              => 'https://login.windows.net/common/oauth2/authorize',
    'urlAccessToken'            => 'https://login.windows.net/common/oauth2/token',
    'urlResourceOwnerDetails'   => 'https://outlook.office.com/api/v1.0/me'
]);

当我运行项目时,出现以下错误:

Fatal error: Uncaught Error: Class 'Stevenmaguire\OAuth2\Client\Provider\Microsoft' not found in C:\xampp\htdocs\microsoftToDo\src\microsoft.php:12 Stack trace: #0 {main} thrown in C:\xampp\htdocs\microsoftToDo\src\microsoft.php on line 12

我的问题是什么?提前谢谢。