Here is my PowerPoint that I planned to present during the workshop: PHP Form Validation PowerPoint
I must make 2 disclaimers. One, you should type F5 to view this as a PowerPoint, or some slides will not make sense (I overlapped some code and animated the presentation).
Two, the Powerpoint is just an introduction to form validation. The content I present is only at a hobbyist level at best, this is not meant to cover all aspects of security. Trying to create your own email processor would most likely lead you open to all kinds of attacks. If you really want a decent PHP form processor, I highly recommend you look into Tectite Forms.