In my case of SoapClient, the request XML should look like this: 

```
<SOAP-ENV:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:SOAP-ENV="http://www.w3.org/2003/05/soap-envelope">
<SOAP-ENV:Body>
    <SoapFunction xmlns="http://services.***/">
        <prop1>value1</prop1>
        <prop2>value2</prop2>
        <prop3>
            <KeyValuePair>
                <Key>string</Key>
                <Value>string</Value>
            </KeyValuePair>
            <KeyValuePair>
                <Key>string</Key>
                <Value>string</Value>
            </KeyValuePair>
        </prop3>
    </SoapFunction>
</SOAP-ENV:Body>
</sSOAP-ENV:Envelope>

```

I could build prop1 and prop2 correctly by the following code: 

```
$parameters = array(
    'prop1' => value1,
    'prop2' => value2
);
$request = array($parameters);
$client->__soapCall('SoapFunction', $request);

```

But how could i build property prop3, especially construct type **KeyValuePair** which is defined in the WSDL file