I just noticed today that a few days ago, WSO2 released the final version 1.0.0 of their WSO2 Web Services Framework for PHP, or WSO2 WSF/PHP in short. I've worked with some of the beta versions and really liked them.
Also, WSF/PHP is backward-compatible with PHP5-SOAP, although this feature is still marked as experimental.
As usual, hosters will be rather hesitant to install a third-party extension for their customers, so not everybody will be able to use this extension. But if you need some of the aforementioned features and would like to reduce the hassle involved in implementing the various standards, you should definitely try out this framework.