There is a new Project Zero application which will scan your application and tell you whether it thinks it will run on Project Zero. The way it does this is to extract information from the Project Zero PHP parser - for instance it finds out the names of functions that are declared in the application and compares them with the names of functions that are invoked.

The scanner looks through the code and, when it finds a function that's not user-declared, checks it against the Project Zero PHP functionality to make sure it will work.

The Zend Engine provides an extension API. This allows anyone to write classes, functions, constants and much more that plug in to the php.net runtime. Taking a peek at the php.net source code in CVS reveals just how many extensions there are.

[...] Zero has a very similar architecture that separates engine and extension. The main difference is that the core PHP language engine is written in Java. Zero also has a comprehensive API called XAPI-J that allows Java extensions to be written for the Zero PHP runtime.

The main difference between the two is the obvious recompile that the Project Zero extensions will have to go through (via JNI) to work correctly with their version of the core. This allows it to be able to use just about any PHP extension out there and saves a lot of work on recoding the great functionality already there.

Project Zero provides an environment for the rapid development of interactive Web applications based on popular Web technologies such as PHP. This tutorial demonstrates how easy it is to get started with Project Zero, from installing the development tools to constructing an Ajax Web 2.0 sample using PHP as the back-end scripting language. Exporting an application is covered on the way, together with examples of debugging and extending a Web 2.0 application.

It walks you through the installation, developing two simple applications with HTML and Javascript and include the Dojo library for extra functionality. You'll have to have an IBM ID (free registration) to check out the tutorial, though.