SDK to communicate with Amazon S3 SOAP Web service - Amazon S3 SOAP API
Official reference guide on http://docs.aws.amazon.com/AmazonS3/latest/API/IntroductionAPI.html
Learn how to use it on https://www.wsdltophp.com/Blog/Retrieve-your-Amazon-S3-Buckets-list-using-the-Amazon-S3-SOAP-API-and-WsdlToPhp