I need to send an xml document to a web service but keep getting fatal errors.

The error I recieve is

PHP Code:
Fatal errorUncaught SoapFault exception: [soap:ServerServer was unable to process request. ---> Object reference not set to an instance of an objectin C:Program FilesApache GroupApache2htdocsweb_servicesvalidationindex.php:40 Stack trace#0 [internal function]: SoapClient->__call('MedinSchematron...', Array) #1 C:\Program Files\Apache Group\Apache2\htdocs\web_services\validation\index.php(40): SoapClient->MedinSchematronValidation(Array) #2 {main} thrown in C:\Program Files\Apache Group\Apache2\htdocs\web_services\validation\index.php  on line 40 
I have been reading lots on this and can not find a sloution.

One article send I should try wrapping my XML in cdata but that does not work.

This is my latest effort, but I have also tried without cdata tags, and passing the xml as a string without assigning it to an array
PHP Code:

$xml_file 
file_get_contents('dataset.xml');

$xml_string '<![CDATA['.$xml_file.']]>';


// Assign the xml string to the parameters
$parameters = array(
                
'xml' => $xml_string
);

// Call the validation method
$client->MedinSchematronValidation($parameters); 
We are hosting the web service but it is not written in C#.

The method I am calling is from Validate.cs and looks like this.

Code:
    /// <summary>
    /// Validate for MEDIN constraints
    /// </summary>
    /// <param name="xml">XmlDocument containing XML to validate</param>
    /// <returns>XmlDocument containing Schematron Validation Report Language (SVRL)</returns>
    [WebMethod(Description = "Validate XML against the MEDIN profile constraints Schematron schema", BufferResponse = true)]
    public XmlDocument MedinSchematronValidation(XmlDocument xml)
    {
        try
        {
            // Check that the HTTP context is not null
            if (HttpContext.Current == null)
                throw new ApplicationException("An attempt has been made to access the server outside a valid HTTP context.");

            // Do the schematron validation
            return this.SchematronValidationMethod(xml, SchematronSchemaType.medinSchematron);
        }
        catch (Exception ex)
        {
            return ServiceException.ThrowSchematronException("An error occured: " + xml.ToString());
        }
    }
Any help would be very much appreciated.

if I need to post anymore information please let me know.

Thanks for any help.