This is a modern alternative to https://github.com/membersuite/sdk-php
MemberSuite's PHP SDK was an outsourced project to smartData and is not supported.
This API client uses the built in SimpleXML, OpenSSL, and SoapClient extensions instead of raw requests, outdated libraries, and other bad things.
composer require ethosce/membersuite
See https://github.com/ethosce/membersuite/blob/master/example.php