Asad's latest article shows us how easy Web Services can be employed using a combination of ingredients, including PHP and GD. Using an example Web Service, Asad shows us how to deploy our own. So, if you're interested in learning a little bit more about this so-called "phenomenon", be sure to have a read.
Cooking With Web Services: PHP & GD - PHP, GD, and NuSOAP (Page 3 of 5 )
PHP GD provides graphical functions for creating images at runtime. There is also another library set called JpGraph; however, in this article we will use the GD library. Constructing graphs with GD is fairly simple and straightforward. You need PHP 4.3.2 or higher to use GD. Run PHP.EXE –m to ensure the GD module is loaded with your current PHP engine. If GD is not installed this article provides a detailed installation guide. In this article we will use the following four functions of the GD library (you may find detailed descriptions of these functions from the PHP manual):
ImageCreate(),
ImageColorAllocate(),
ImageLine(),
ImageString()
You also need PHP NuSOAP to consume Web Services. Download the necessary files (basically it is a single file NuSoap.php) and copy this file to the appropriate folder.
Web Services 
Generating Images on the Fly With PHP
