There are many PHP CMS Frameworks which provide the capability to easily handle a quality web site which needs daily maintenance. Drupal , Joomla are two such CMS frameworks. These are grate tools for building web sites and managing content. How ever they are functioning in isolation. When a site grows big, these systems happen to have a lot of valuable data that needs to be integrated with other enterprise systems in order to add business value.
For example consider an enterprise which has build its main web site using one of these tools and has many registered users to this site. Now the enterprise wants to incorporate these users to another application which the enterprise is running, because it wants to provide single sign on capability without having make the users go through another tiresome registration workflow. Also think a scenario where this other system is running on java or .net.
One obvious solution would be to share the database used by the CMS framework for the other application. But such a thing would add many complexities and would require one of the systems to be changed which is not doable in many situations. Now if the other system provides some programmable API or a web services API, then there is an elegant way to solve this integration problem.
With the availability of WSF/PHP Data Services solution, now you have an easy way to overcome such problems. You can exposed data manipulation operations of the CMS database as web services using WSF/PHP Data Services. Now the two systems can talk to each other using their respective web services and clients, and you have a beautifully integrated solution.