The following is a sample SOAP 1.1 request and response.:
POST /atservices/1.5/atws.asmx HTTP/1.1
Host: webservices2.autotask.net
Content-Type: text/xml; charset=utf
Use the PHP native SoapClient along with the service WSDL, like so:
$atservices_wsdl = "https://www.autotask.net/atservices/1.5/atws.wsdl";
$atservices_client = new SoapClient($atservices_wsdl);
$zone_info = $atservices_client->getZoneInfo("SomeUserName");
print_r($zone_info); // review the returned object converted from SOAP response.
echo $zone_info->DataBaseType; // this might work if it's not behind a Response object.
At the very least, you should be aiming for something like this. More can be found here.
$soap = new SoapClient('link/to/.wsdl');
$result = $soap->__soapCall('getZoneInfo', array('UserName' => $username));
var_dump($result);