This talk is a complete overview of the theory, tools and some tips for dealing with consuming web services of all kinds. It covers service types, data types, and different ways of working with these from PHP, with examples. I had many more attendees in this session than I expected, and it was a fun talk to give.

Blog: PHP Barcelona 2009 Round Up

http://www.slideshare.net/lornajane/working-with-web-services