`$client = new SOAPClient('http://devapi.stellatravelgateway.stellatravelservices.co.uk/DirectoryService.svc?singleWsdl',
 array(
    'location' => 'http://stellatravelgateway.stellatravelservices.co.uk/DirectoryService/IDirectoryService/Authenticate',
    'trace' => 1,
    'style' => SOAP_RPC,
    'use' => SOAP_ENCODED,
  )
 );

$request = array(
  "BranchCode" => "xxx",
  "UserName" => "xxx",
  "Password" => "xxx",
  "Application" => "xxx",
  "Client" => "x",
  "BranchID" => 0
);

$result = array();

try {
    $result = $client->__soapCall('Authenticate', $request);
} catch (SoapFault $e) {
    echo "SOAP Fault: ".$e->getMessage()."<br />n";
}

 echo "<pre>";
 echo htmlspecialchars($client->__getLastRequestHeaders())."n";
 echo htmlspecialchars($client->__getLastRequest())."n";
 echo "Response:n".htmlspecialchars($client->__getLastResponseHeaders())."n";
 echo htmlspecialchars($client->__getLastResponse())."n";
 echo "</pre>";

 var_dump($result);`

POST /DirectoryService/IDirectoryService/Authenticate HTTP/1.1
Host: stellatravelgateway.stellatravelservices.co.uk
Connection: Keep-Alive
User-Agent: PHP-SOAP/5.5.38
Content-Type: text/xml; charset=utf-8
SOAPAction:"http://stellatravelgateway.stellatravelservices.co.uk/DirectoryService/IDirectoryService/Authenticate"
Content-Length: 367


<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ns1="http://stellatravelgateway.stellatravelservices.co.uk/DirectoryService"><SOAP-ENV:Body><ns1:Authenticate/><param1>xxx</param1><param2>xxx</param2><param3>xxx</param3><param4>x</param4><param5>0</param5></SOAP-ENV:Body></SOAP-ENV:Envelope>

Response:
HTTP/1.1 404 Not Found // Here
Content-Type: text/html
Server: Microsoft-IIS/7.5
X-Powered-By: ASP.NET
Date: Mon, 19 Mar 2018 13:34:51 GMT
Connection: close
Content-Length: 1245

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:dir="http://stellatravelgateway.stellatravelservices.co.uk/DirectoryService">
    <soapenv:Header/>
      <soapenv:Body>
         <dir:Authenticate>
           <dir:authenticateRequest BranchCode="xxx" UserName="xxx" Password="xxx" Application="xxx" Client="xxx">
           <dir:BranchID>xxx</dir:BranchID>
          </dir:authenticateRequest>
        </dir:Authenticate>
      </soapenv:Body>
   </soapenv:Envelope>