Designed primarily for web scripting, it's no wonder that PHP is one of the most important workhorses of the Internet. And, a lot of my Internet experience having come from webmastering, it's no wonder that I've spent plenty of time working on things in PHP. Of course, the majority of these things are user-invisible, single-purpose things - stuff like the original site infrastructure on the Merton JCR site (which has since been replaced), or the original article management system at the Owl Journal. Still, there have been one or two things that you might find useful:
Oxford Date Converter
The online version of programs I originally wrote in C / C++, this is written as a library of sorts that can be incorporated into other projects. Termcards and scheduling systems, for instance, so that Oxford dates and real-world dates don't need to be individually worked out. This was first written for Merton JCR's website, and unless things have changed since I was webmaster, can still be seen in action (as the underlying library, not the interface) here.
Licensed under the GNU General Public License.
Download/ View Source - it's labeled with an additional
.txt extension to allow it to render in a browser.
Related Items By Category Module
Written as a modification and extension of the standard related items module from the Joomla! content management system (version 1.0.x), this module is capable of limiting its search to one or more Joomla! content categories. You can download it here, and it should be easily installable from the Joomla! admin interface. Being a modification of GPLed code, it is of course licensed under the GNU General Public License.