About PHP workflow engine, in addition to three major open source: Porcessmaker (ranked first, because it has a drag-and-drop graphical definition Interface), Radicore (based on Petri NET) and Cuteflow, there is another unknown, but also very powerful open source, Called ezerphp.
Ezerphp's homepage: http://code.google.com/p/ezerphp/EzerPhp, like Porcessmaker, is a BPM engine. Also, it is based on the BPEL language. Therefore, there are two ways to support BPEL in this open source code: the first, using XML (BPEL). The second type, use the database. Because, using the database abstraction layer propel, so, can support: Mysql,oralce and many other mainstream databases. Ezerphp: is a client server horizontal type. At the same time, the server-side ezerphp is the process of memory and can automate workflow. The biggest feature of ezerphp is simplicity. Can be embedded directly into any application. You can use BPEL to define a process through a database, or XML. Then start the service-side resident process. This is followed by a client call. You can create a process client directly, or you can use the socket client. ezerphp: The premise of using it: Understand: BPEL, understand propel (about its configuration), can read the root directory of the Readme file (this is its entire document), if it can be installed successfully, and can correctly run all the instance code, then, then, You can add a workflow to your app. Although there is no porcessmaker, there is a drag-and-drop graphical definition interface, or like Radicore, is a development framework, but as an application of the third-party components, simple, easy to use, it is a very good choice. Other Workflow engines: Http://www.oschina.net/project/tag/129/workflow
About PHP's Workflow engine