Spectator is a XUL application, which should make it cross platform. I have tinkered a bit with XUL before, but not a full application. [...] So what can spectator do? Mind that this is a first version and I really just meant it as a proof of concept. I think I got a bit further than that, but it probably still has a few bugs. Still, with the current version, you can step through a program, set breakpoints and inspect the stack. Really all you would expect from a debugger.

You can grab the latest version from the subversion repository on the Google Code website.

2 years after begining, I'm happy to announce you the "Beta" release of the Gul 2.0 project, the XUL parser for PHP GTK (97% released). I have to do lot of things, but i think it looks like something.

You can find out more information about the project on the Gul project page over on the redsoft.net domain (including the downloads).

phpPatterns brings another tutorial to the PHP community today with this guide to creating XUL applications with the help of PHP.

XUL, or the XML User Interface language, is the common thread running through all Mozilla-powered applications - both desktop and web-based. XUL is a way to describe an application's user interface using XML. XUL is similar in many ways to HTML, while borrowing from, yet not exactly imitating its syntax.

To start off with, we need a simple XUL file that contains a form. This form could consist of anything, but for this example, I will be using a simple Login form that you might be familiar with while building web applications.

They provide the full code of the XUL, PHP, and Javascript to make everything worrk together. They explain how it all goes together and even some of the basics of XUL.