Error with SPROC calling a web service

Ok,
so I created a webservice in .net, I have successfully accessed and returned data from a particular function in an asp.net and vb.net application.
So I wanted to try my hand at php.
After much work I am stumped at this error.

Code:

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Uncaught SoapFault exception: [soap:Server] Server was unable to process request. ---> Procedure 'getSRCourseVersionCourseKey' expects parameter '@CourseKey', which was not supplied.

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This is referring to my stored Procedure, which obviously is not getting the parameter it needs to execute properly.
My php code is below.
I've checked the name of the parameter but math151 is not getting in to the sproc. no problems with my .net clients on the same call.
Some help would be great! :)

Code:

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<?php
require_once('nusoaplib/nusoap.php');

$wsdl="http://xxx/myService.asmx?WSDL";
$client=new soapclient($wsdl);

$results = $client->__Call('LoadLatestVersionByCourseKey',array('pCourseKey'=>'math151'));                 

echo "<font color=red>";
echo $results->GetTermsResult;
echo "</font>";

                echo "<pre>";
                var_dump($results);
                echo "</pre>";

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