Nusoap is discontinued project (not actively developed since 2007). ZendSoap is probably the best way to go.

Bottom line: I suggest Zend Soap. To explain further...

NuSOAP Cons

1. Is written entirely in PHP. This means it s relatively slow.
2. Was indeed recently updated, but it s still pre-1.0, and prior to that update, it hadn t been updated since 2007. Thus, I wouldn t say it s a real active project.
3. Perhaps fixed now, but when I ve used it in the past, it s conflicted with PHP soap (e.g., using the the same type names), and it s not fared well under E_STRICT, which I use for all development.

NuSOAP Pros

1. Handles WSDL generation for you, saving you this tedious, error-prone task.
2. Is flexible with the features it supports.

PHP SOAP Cons

1. Provides no way to generate a WSDL.
2. Is a pain to use with SOAP headers.

PHP SOAP Pros

1. Is written in C and compiled, and so runs very, very fast.
2. Is very simple to use without the need to use third-party code libraries.
3. Integrates nicely with other PHP 5 features, such as SimpleXML.

Zend Cons

1. Requires use of a third-party code framework. The framework is modular, so you can pick out the parts you need, but it s much easier just to bring in the whole thing. (Though, this does not mean you need to use the framework for the rest of your app - using just the SOAP bits is trivially easy.)

Zend Pros

1. Builds onto PHP SOAP, rather than replacing it. Thus, you get much of the speed advantage, plus extra features.
2. Fills in most of the holes in PHP SOAP, such as easy WSDL generation and easier configuration.
3. Integrates very nicely with the rest of PHP 5.
4. Is undergoing very active development with support from some major industry heavyweights.

http://www.php.net/manual/en/class.soapclient.php

it isn t discontinued. there is a current version 0.9.5 for download, from 2010-04-26 at http://sourceforge.net/projects/nusoap/files/

and before there was updates from cvs

nusoap support php4

zend soap support php5