Zend Framework's new release 1.6 is in it's RC1 stage now. It has got many exiting features, including one of the much waited WSDL auto-generation using Zend_Soap_AutoDiscover class. It will automatically generate WSDL based on your class definition based on PHP Documentation.
I am not sure why it is taking long with PHP to have WSDL auto-generation feature? May be loose typing..!
Anyway current implementation of Zend's WSDL generation with Zend_Soap_AutoDiscover doesn't seems to be perfect. It is having issues with Complex Type. Although you can manually generate WSDL with the help of Zend_Soap_Wsdl.
When I tried with AutoDiscovery feature results were surprising for Complex Type, behavior of generator was weired. Let's hope that Zend will fix issues with this great feature before their final release. Documentation is also in it's building stage and needs more examples and better compilation. Download Zend Framework from here, and try with tar.gz, it looks like zip is not working for me (more than once) with current compilation due to some reason.
Previously I have used WSDL generator class from jool.nl, it was quite handy and easy to configure and uses Reflections to generate WSDL from PHP Docs just like Zend Framework.