This next script is a simple PHP Guestbook script that I helped write for a friend who needed a replacement to the Gospelcom Guestbook script, which is very powerful, but does have a few small limitations.
If you can use the Gospelcom Guestbook script, I recommend it highly! However, if you need a custom solution, this will hopefully at least point you in the right direction.
Example PHP Guestbook Script Example Form for above script