We initiated a new open source project called Jackalope. Its purpose is to bring JCR via Jackrabbit to the PHP world. [...] JCR provides a great standardized storage for hierarchical content and supports some nice features like full text search, versioning, transactions, observation, and more. Our main goal is to create a PHP Connector for Jackrabbit without using any Java.

To accomplish this, they're doing things in two steps. First, they've created a setup with the Java bridge (from Zend Server) to make the connection back to the Jackrabbit server and making writing tests to that API. The second step is to swap out the Java bridge with the Jackalope connection piece. You can check out the current state of the project on its Github page or come and ask questions of the team on the Freenode IRC network (#jackalope).