First web service howto

Hi, Ok i have made up my mind that i will use PHP. Now i need to get together all the tools of the trade and make them work. I am using apache on a Kubuntu box. and i have PHP5 installed..

What else    do i need to make the web service.

Do i need nuSOAP or PEARS? The first web service that i will be making will take a URL as input argument and will return a boolean YES or NO. I would appreciate if some one can give a code snippet specially the part related to SOAP and wsdl. Regards -- "Windows [n.] A thirty-two bit extension and GUI shell to a sixteen bit patch to an eight bit operating system originally coded for a four bit microprocessor and sold by a two-bit company that can't stand one bit of competition."