$accessToken = 'Bearer xxxxx'; // obtenu via Azure OAuth2

$url = "https://yourtenant.sharepoint.com/sites/yoursite/_api/web/GetFileByServerRelativeUrl('/sites/yoursite/Shared Documents/test.docx')/\$value";

$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    "Authorization: $accessToken",
    "Accept: application/octet-stream"
]);
$response = curl_exec($ch);
curl_close($ch);

// Sauvegarder localement
file_put_contents("fichier.docx", $response);