This week I managed to listen to most of Veronica Gomes' and Dennis Allen's Chat with the Labs on integrating Informix with SolidDB and was glad I did. It was packed with useful information.
Incidently, if you ever need slides for any of the chat with the lab series, including the latest one, you can download them from here:http://www.ibm.com/software/data/informix/labchats/. The audio replays appear here after some time as well.
If you're interested in developing PHP applications that integrate with SolidDB, you could do worse than read this developerWorks article: Building dynamic Web page applications using PHP and IBM solidDB by Abhinay Nagpal, Gaurav Mehrotra andYogesh Gawali.