I realise I haven't thrown my PHP readers a bone for a while. Lately, unfortunately, all my experience has been with how not to do things. Some of this has been my own fault, but a really healthy percentage has come because I am maintaining one horrible project and rewriting another even more horrid. So, a few pointers for you l3et coders out there: Don't do any of this stuff.
Items on the list include less than thought out design and a lack of knowledge about how to properly use a database.