XML: The Bridge Between GWT and PHP
http://www.ibm.com/developerworks/xml/library/x-gwtphp/index.html?S_TACT=105AGX06&S_CMP=EDU

Kereki, Federico
IBM
2009

Abstract:

Google Web Toolkit (GWT) applications, apart from connecting to servlets in time-honored Java fashion, can also use PHP Web services to send and receive data in XML. You'll explore methods to generate XML documents and process them, both in the Java language and in PHP.