Rending Images into a circle - GD

Okay, this is hard to explain, however, im sure there is a mathematical word for doing it, and calculating it.

I have an array of images, like so:

etc.

Now, I need to use GD library to render these in a circle. (As in each image is rendered around, next to each other, in a circle shape)

It must render the images in a circle and if there are more images, it renders them closer together.

Any help on this would be great!

Thanks