Zeev Suraski has a new post over on his blog talking about "PHP 5's SOAP extension and SalesForce".

In the last few days I've been working on a piece of code in PHP that had to integrate with SalesForce. During the course of this work I bumped into some minor annoyances (or rather, a minor annoyance) with ext/soap, which I was able to quickly fix thanks to Dmitry's excellently structured code.

For those who are interested, you can now set custom SOAP headers using SoapClient::__setSoapHeaders(). This will cause SoapClient to send the headers on every subsequent access to a web service, conducted through the relevant SoapClient object.

He gives the code for his connection to the SalesForce API, but not much else. It's pretty straight forward, though, and anyone familiar with the SOAP libraries/functionality in PHP5 shouldn't have a problem implementing it...