One page php script needed for...

I would like someone to write a simple php code that makes uploaded image file by user to round shape and then marge the uploaded file to other image file so that uploaded image is set within predefined area of other image. attached is sample image, in which round white circle is, so if a user uploads an image, the given image should be filled in sample image's white circle.

Hope things are pretty clear, if not, please ask question.