CakePHP4でトランザクションを使う！

use Cake\Datasource\ConnectionManager;
use Cake\Core\Exception\Exception;

$connection = ConnectionManager::get('default');
$connection->begin();

$users = TableRegistry::getTableLocator()->get('users');
$articles = TableRegistry::getTableLocator()->get('articles');

$users->setConnection($connection);
$articles->setConnection($connection);

try {
    $user = $users->newEmptyEntity();
    $user->email = '[e-mail]';
    $user->password = 'passpass';
    $users->save($user, ['atomic' => false]);

    $article = $articles->newEmptyEntity();
    $article->user_id = $user->id;
    $article->title = 'タイトル';
    $article->body = '本文';
    $articles->save($article, ['atomic' => false]);

    $connection->commit();
} catch (Exception $e) {
    $connection->rollback();
    throw $e;
}