New from NETTUTS.com there's a recent tutorial showing you how to use the GD graphics library (bundled with PHP) to resize images on the fly.

Ever wanted an all purpose, easy to use method of resizing your images in PHP? Well that’s what PHP classes are for – reusable pieces of functionality that we call to do the dirty work behind the scenes. We’re going to learn how to create our own class that will be well constructed, as well as expandable. Resizing should be easy.

The simple eleven-step process (don't worry, it sounds worse than it is) has you go from a basic image and, with the help of a custom PHP class, create a resized image based on a type such as "landscape", "auto" or "exact". Full code is included for you to cut and paste or you can download the source and have the full code ready and waiting.