In a new post to the PHP-GTK Community website today, they've spotlighted a handy new PHP-GTK2 application - VIES client.
The VIES client allows querying of the EU VAT database system to check the validity of VAT numbers. This is a fairly essential function to businesses within the EU, and avoids having to use the standard browser-based service, by relying on SOAP RPC, which allows access from within any application.
The application is mainly intended to be a learning tool, showing how to create a SOAP connection inside of an app. The application's page (on the Riff Blog) steps through it all to give you a better understanding.