PSX is a framework for developing dynamic Web sites in PHP. The goal of PSX is to help you develop RESTful APIs serving Web standard formats like JSON, XML, Atom, and RSS. It has a focus on social technologies and provides classes to use and implement OAuth, OpenID, Opengraph, Opensocial, Opensearch, PubSubHubbub, Atom, and RSS.
Fulworx is a REST framework that uses simple annotations of XWork "Action" implementations to expose restful interfaces. Similar to Struts, Fulworx sits as a controller on top of Restlet. Each action is attached as a resource using Restlets. Standard resources are represented by default as XML (or JSON) using JAXB, but any representation may be specified. Actions may be used in other frameworks such as Struts and Webwork, since they're just XWork implementations.