Content repositories can be useful for your application. In the PHP track of FrOSCon on Aug 22nd there will be a talk about this: Midgard2: Content repository for your PHP application
Content repositories allow you to separate the actual front-end of your application from background processing tools. More than just their underlying databases, they impose common rules for data access, and keep multiple applications up-to-date on data changes through signaling. Midgard2 provides a flexible content repository that avoids the restrictions of the traditional ORM approach. And not only your PHP web application, but also to possible Python, Objective-C and C# tools you use.
This enables you to split applications into smaller, easily maintainable and scalable pieces that can be run on different systems and platforms as needed. In addition to web, the Midgard2 library can be used for desktop and mobile application development, building software that synchronizes with web services. It is based and engineered fully on the top of the desktop (GNOME) software stack. Being highly modular and having very little dependencies it scales from a note taking application to a full-blown CMS system. Combined with advanced replication capabilities it allows you to synchronize data between offline and online instances of your service.