Might be Stockholm syndrome, but I actually kinda like SOAP...
I used wsdl2phpgenerator for a recent project, and it saved me a load of time. Just run the WSDLs through that and you can get started building your own classes on top of the auto-generated ones. I didn't find a need for any of the other SOAP wrappers out there, the PHP built-in classes and the auto-generated wsdl2php classes are good enough to extend and build upon.
You can use SoapUI to fire off test requests.
Generally, I skip the capturing part if I have access to the API. I'll use SoapUI (http://www.soapui.org/), point it toward the correct end-point and let it stub out the requests. I'll get my payload right in SoapUI and then convert it over to SOAP::Lite.
When I do need to see data going back and forther (generally HTTP calls) I'll bust out Fiddler, a local HTTP(S) sniffer: http://www.telerik.com/fiddler
But there is also other good info in this thread including an alternative to SOAP::Lite.
You are up to something there. Not exactly an easy project to start since SOAP service endpoints are kind of complex to work with.
To start you may possibly want to get some tools to easy exploring the API. I would recommend using SoapUI for which you can get a free version which would be more than enough for a start.
You would first load their API description file (find here. store it on disk. In SoapUI create a new soap project, give it a name and for 'initial WSDL' just use the file you saved. It will generate a list of SOAP calls. This gives you a nice overview and you could actually use the tool to send some test requests.
The give sample codes for C# and Visual Basic. You could use mostly any programming language but would have to write your own code. I have used SOAP APIs from Ruby on Rails. But I'm quite experienced and would not exactly recommend that path for somebody new. (Though it's definitely possible to use Ruby on Rails for that)
Also it may be difficult (or even impossible) to test much without having actual data (especially a valid login). Not sure how much data this test system provides. Though short look it seems it could work well enough.
I'm at work right now so don't have the time to write much more. Maybe have a look at the tool and see how far it can get you.
SOAP services provide a WSDL file which exactly describes what you can do with it and how to call it. Find this file then stuff it into some generic client like soapUI, it will generate and show you the exact http calls you need to make.
Example with some random service: http://www.wurvoc.org/doc/oum/ch05s03.html
Just posted a quick response to your SO question recommending http://www.soapui.org/. It's one of the best tools I've seen to consuming SOAP APIs. Have not tried their just released version 5.0 but 4.0 was great!
It should help you see what you're sending and what's being returned quickly to help debug your issue.
Not sure, unfortunately it appears to work fine for me: http://imgur.com/a/E6f1o
I did see this forum post that looked somewhat related to your problem.