Send an email using PHP with Microsoft OAuth 2.0 authentication

To send an email using PHP with Microsoft OAuth 2.0 authentication, you will need to:

1. Register your application with Microsoft and get the necessary credentials (client ID and client secret). You can do this by following the steps outlined in the Microsoft documentation: https://docs.microsoft.com/en-us/azure/active-directory/develop/quickstart-register-app
2. Install the PHP OAuth 2.0 client library. You can use Composer to install the PHP OAuth 2.0 client library:

composer require league/oauth2-client 

Use the OAuth 2.0 client library to get an access token. You can use the following code to get an access token:

use LeagueOAuth2ClientProviderMicrosoft;
$provider = new Microsoft([
    'clientId' => 'your-client-id',
    'clientSecret' => 'your-client-secret',
    'redirectUri' => 'http://your-redirect-uri/'
]);
// If the user has not authorized your app, redirect them to the Microsoft login page
if (!isset($_GET['code'])) {
    $authUrl = $provider->getAuthorizationUrl();
    header('Location: '.$authUrl);
    exit;
// If the user has authorized your app, get an access token
} else {
    $accessToken = $provider->getAccessToken('authorization_code', [
        'code' => $_GET['code']
    ]);
}
 

Use the access token to send an email using the Microsoft Graph API. You can use the following code to send an email using the Microsoft Graph API

use GuzzleHttpClient;
$client = new Client();
$response = $client->post('https://graph.microsoft.com/v1.0/me/sendMail', [
    'headers' => [
        'Authorization' => 'Bearer '.$accessToken,
        'Content-Type' => 'application/json'
    ],
    'json' => [
        'message' => [
            'subject' => 'Email subject',
            'body' => [
                'contentType' => 'Text',
                'content' => 'Email body'
            ],
            'toRecipients' => [
                [
                    'emailAddress' => [
                        'address' => 'recipient@example.com'
                    ]
                ]
            ]
        ],
        'saveToSentItems' => 'true'
    ]
]);