In addition to XML and JSON outputs, Yahoo! has now added Serialized PHP as an output format to their Travel, Search, and Maps Building Block Web Services. They now have a PHP Developer Center too.
We're sending out Serialized PHP love via our Yahoo! Web Services. In addition to returning XML, our Travel, Search, and Maps Building Block Web Services now return Serialized PHP. Serialized PHP is PHP data structures encoded as text. It's easily consumed by PHP, and all you have to do is add the output=php parameter to have your web services request return it.
Yahoo! adds Serialized PHP ouptput suuport to its Web Services