This chapter showed how to use Web services with the brand-new SOAP extension for PHP 5. Although underlying technologies such as SOAP and WSDL are quite complex, their usage with PHP is rather easy. Except for the WSDL creation, the rest of the task can be done in very few lines of PHP.
For further information, you might want to have a look at the various standards involved. The SOAP home page at W3C is http://www.w3.org/TR/soap/, and the WSDL standard can be found at http://www.w3.org/TR/wsdl (without a trailing slash after wsdl!). For UDDI, a specific Web presence exists at http://www.uddi.org/.