(Applet) Saving image to file on server?

Hi, i have a simple drawing applet which allows you do draw lines on a canvas. Now I would like to be able to save that drawing to a file on the server. But, because of the Java applet security restrictions it can't just be written to the server's (or even client's or any other) file system.

To get around this problem I was thinking about sending data back to a PHP script on the same server.

Any ideas on how to best do such a thing?