This is my code:

<?php
error_reporting(E_ALL);
//new instance of soapClient pointing to Ebay finding api
$client = new SoapClient("http://developer.ebay.com/webservices/finding/latest/FindingService.wsdl"); 

//attach required parameters to soap message header
$header_arr = array(); 
$header_arr[] = new SoapHeader("X-EBAY-SOA-MESSAGE-PROTOCOL", "SOAP11");
$header_arr[] = new SoapHeader("X-EBAY-SOA-SERVICE-NAME", "FindingService");
$header_arr[] = new SoapHeader("X-EBAY-SOA-OPERATION-NAME", "findItemsByKeywords");
$header_arr[] = new SoapHeader("X-EBAY-SOA-SERVICE-VERSION", "1.0.0");
$header_arr[] = new SoapHeader("X-EBAY-SOA-GLOBAL-ID", "EBAY-GB");
$header_arr[] = new SoapHeader("X-EBAY-SOA-SECURITY-APPNAME", "REMOVED"); 
$header_arr[] = new SoapHeader("X-EBAY-SOA-REQUEST-DATA-FORMAT", "XML");
$header_arr[] = new SoapHeader("X-EBAY-SOA-MESSAGE-PROTOCOL", "XML");

$test = $client->__setSoapHeaders($header_arr); 

$client->__setLocation("http://svcs.ebay.com/services/search/FindingService/v1");//endpoint

$FindItemsByKeywordsRequest  = array(
    "keywords"      =>  "potter"
);

$result = $client->__soapCall("findItemsByKeywords", $FindItemsByKeywordsRequest);

//print_r($client->__getFunctions());
//print_r($client->__getTypes());
//print_r($result);

?>

And this is the error I receive:

Fatal error: Uncaught SoapFault exception: [axis2ns2:Server] Missing SOA operation name header in C:\xampplite\htdocs\OOP\newfile.php:25 Stack trace: #0 C:\xampplite\htdocs\OOP\newfile.php(25): SoapClient->__soapCall('findItemsByKeyw...', Array) #1 {main} thrown in C:\xampplite\htdocs\OOP\newfile.php on line 25

It doesnt make sense, I have already set the operation name in the header of the request... Does anyone know what is wrong here?