PHP Soap function coming up as 'No such operation' even though in function list

Attempting to get SOAP calls from a wsdl working within PHP. Querying an WebCT axis server wsdl and I get back that it has the following functions:

Array
(
    [0] => SessionVO login(string $user, string $password, string $learningContextID)
    [1] => void logout(SessionVO $session)
    [2] => ArrayOf_xsd_long getLearningContextIDs(SessionVO $session)
    [3] => ArrayOf_xsd_long getTemplateIDs(SessionVO $session, long $learningContextID)
    [4] => ArrayOf_xsd_string getRoleIDs(SessionVO $session, long $learningContextID)
    [5] => LearningCtxtVO getLearningContext(SessionVO $session, long $learningContextID)
    [6] => ArrayOfLearningCtxtVO getLearningContextList()
    [7] => RoleVO getRoleDefinition(SessionVO $session, string $roleID)
    [8] => ArrayOfRoleVO getRoles(SessionVO $session, long $learningContextID)
    [9] => ArrayOfSourcedIDVO getLearningGroupsByIMSId(SessionVO $session, SourcedIDVO $imsid)
    [10] => ArrayOfSourcedIDVO getLearningGroupsByLCId(SessionVO $session, long $lcid)
    [11] => ArrayOfSourcedIDVO getLearningGroupMembers(SessionVO $session, long $lcid)
    [12] => TemplateVO getTemplate(SessionVO $session, long $learningObjectID)
    [13] => long getLearningContextIdByPath(SessionVO $session, string $path)
    [14] => long getLearningContextIdBySourcedId(string $source, string $id)
    [15] => string getReleaseVersion()
    [16] => boolean isCompatibleWith(string $version)
    [17] => ArrayOf_xsd_long getInstructorPersonIDs(SessionVO $session, long $lcid)
    [18] => long getParent(SessionVO $session, long $lcid)
    [19] => ArrayOf_xsd_long getChildren(SessionVO $session, long $lcid)
)

However when I execute the following function I get back an error of "No such operation 'getLearningGroupsByIMSId'":

function getAllMembers($contextID = -1) {
        try {
            $开发者_StackOverflow社区learingContext = $this->context->getLearningContext($this->session,$contextID);
            print_r($learingContext);
            $groups = $this->context->getLearningGroupsByIMSId($this->session,$learingContext->sourcedID);
            print_r($groups);
            foreach($groups as $group) {
                $members = $this->context->getLearningGroupMembers($this->session,$group->sourcedID->myID);
                print_r($members);
            }
        } catch(Exception $e) {
            print_r($e);
            return false;
        }
        return $members;
    }

Any ideas of why it might not be recognizing that function even though it shows up on the function list? All the other functions seem to work other than that and getLearningGroupsByLCId - both give the same error.