Accessing function/method through cURL - php

Question

If I used SoapClient, my code would look something like this:
$baseurl = 'http://www.webservicex.net/geoipservice.asmx?WSDL';
$client = new SoapClient($baseurl);
print_r($client->GetGeoIP(array('IPAddress'=>'123.45.67.890')));
So using $client, I can access the GetGeoIP method. How would do the same thing using cURL?
So far I've set up the code as:
$curl = curl_init($baseurl);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_HEADER, false);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
$rawPOSTdata = array(
"IPAddress" => "123.45.67.890",
);
// now how do I specify that I want to send $rawPOSTdata to the GetGeoIP() function?
curl_setopt($curl, CURLOPT_POSTFIELDS, $rawPOSTdata);
curl_setopt($curl, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
$response = curl_exec($curl);
Now where and how do I specify the function call GetGeoIP?
EDIT
After extending the SOAP class, this is what I got for $request
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://www.webservicex.net/">
<SOAP-ENV:Body>
<ns1:GetGeoIP>
<ns1:IPAddress>123.45.67.890</ns1:IPAddress>
</ns1:GetGeoIP>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
So if I got this right, I should store this inside a variable and use in the
curl_setopt($curl, CURLOPT_POSTFIELDS, $xml_string) ?

Answer 1

If you download and use SoapClientTimeout, and then simply change the class's __doRequest emthod and include a dump of the $request variable to figure out how SoapClient wraps it:
public function __doRequest($request, $location, $action, $version, $one_way = FALSE) {
echo htmlentities($request);
//...
}
and call it as a regular soap client:
$baseurl = 'http://www.webservicex.net/geoipservice.asmx?WSDL';
$client = new SoapClientTimeout($baseurl);
print_r($client->GetGeoIP(array('IPAddress'=>'123.45.67.890')));
..you'll get your answer:
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://www.webservicex.net/">
<SOAP-ENV:Body>
<ns1:GetGeoIP>
<ns1:IPAddress>123.45.67.890</ns1:IPAddress>
</ns1:GetGeoIP>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>
This entire XML string goes into CURLOPT_POSTFIELDS.