This is the example usage page for PHPImageHandler. Just use the form to select an image and change the current image. With current settings the image has to be at least 250x250 pixels and two sizes will be made alongside the original. One is the 50x50px image, one with 250x250px and the original.
You can purchase the latest version from Gadratilprogramming website.
PHP Image Handler
Clicking the small thumbnail brings up the large image