Alibaba Cloud Classic SDK for Java is supported in PHP 5.6 and later versions. The Classic SDK features high stability. Many existing users are accustomed to using the Classic SDK for development. This user guide is intended for the existing users of the Classic SDK. For new users, we recommend that you use Darabonba SDK for PHP. For existing users, we recommend that you start to use Darabonba SDK for PHP at the earliest opportunity. For more information about the benefits and user guide of Darabonba SDK for PHP, see Get started with Alibaba Cloud Darabonba SDK for PHP.