Often, tutorials covering the GD libraries and it's available functions in PHP will show how to overlay text onto images, manipulate images (resize, flip, rotate, etc) or how to dynamicly generate charts or graphs from numerical data. I have not seen many demonstrating how to combine images (or moreso, placing a transparent forground image over a background image).
Image rotation in PHP is handled by a function called imagerotate(), which takes three parameters (and optionally a fourth, which deals with transparency and is beyond the scope of this guide). The first is the resource identifier which you obtain when you load the original image within your script, the second is the angle which you want to rotate the image and the third parameter is used when the image isn't going to be rectangular, and specifies the colour with which to fill the uncovered areas of the rotated image to make it into a rectangle (since all image formats require rectangular images).
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