So, I googled and found out how to draw an arc: http://www.php.net/manual/en/function.imagearc.php
The only problem is how to write text $ margin pixels from an arc that is curved.
Center aligned @ $ degrees.
Here is an example: http://img194.imageshack.us/img194/3667/scan0001fe.jpg
Let me know if that doesn't make sense.
Here is a simple PHP solution found at http://forums.phpfreaks.com/topic/57542-image-manipulation-skewing-text-text-on-a-curve/
You can try the following: http://coding.derkeiler.com/Archive/PHP/alt.php/2004-12/0061.html
Imagick has built-in curved text support