function DoUpdatePaymentStatus(
    $pp_Version,
    $pp_TxnType,
    $pp_BankID,
    $pp_Password,
    $pp_TxnRefNo,
    $pp_TxnDateTime,
    $pp_ResponseCode,
    $pp_ResponseMessage,
    $pp_AuthCode,
    $pp_RetreivalReferenceNo,
    $pp_SecureHash,
    $pp_ProductID,
    $pp_SettlementExpiry
){

    global $db_obj;
     header("Content-type: text/xml");
    $servername="localhost";
    $username="smsprouser";
    $password="North123";
    $dbname="smspro";
    $db_obj = new mysqli($servername, $username, $password, $dbname);


    $sql = "INSERT INTO transaction_status_log (pp_TxnRefNo, pp_ResponseCode, pp_RetreivalReferenceNo,pp_TxnDateTime)
            VALUES ('$pp_TxnRefNo','$pp_ResponseCode','$pp_RetreivalReferenceNo','$pp_TxnDateTime')";
    if ($db_obj->query($sql) !== TRUE) {

    $sql = "INSERT INTO transaction_status_log (pp_TxnRefNo, pp_ResponseCode, pp_RetreivalReferenceNo,pp_TxnDateTime)
            VALUES ('1','2','3','4')";
    $db_obj->query($sql);

  $response = '<?xml version="1.0"?>';
    $response .= '<response><status>000|status updated successfully|</status></response>';
return $response;     }else{
  $response = '<?xml version="1.0"?>';
    $response .= '<response><status>000|status updated successfully|</status></response>';
return $response;



            }



        // check for required parameter
        $required_params = [
            'pp_Version' => $pp_Version,
            'pp_TxnType' => $pp_TxnType,
            'pp_Password' => $pp_Password,
            'pp_TxnRefNo' => $pp_TxnRefNo,
            'pp_TxnDateTime' => $pp_TxnDateTime,
            'pp_ResponseCode' => $pp_ResponseCode,
            'pp_RetreivalReferenceNo' => $pp_RetreivalReferenceNo
        ];

        foreach ($required_params as $in => $iv){
            if(!isset($iv) or empty($iv)){
                return "012Missing mandatory parameter(s) ".$in;
                exit;
            }
        }


        // some checks before going through the process
        if($pp_Version != '1.1' or $pp_TxnType != 'OTC'){
            return "013Invalid valued for parameter(s)";
            exit;
        }


        // get the payment token from response
        $payment_token = $pp_RetreivalReferenceNo;
        $password = $pp_Password;
        $application_id = $pp_TxnRefNo;

        if($password == "7w9377041a" and in_array($pp_ResponseCode, ['000', '121', '200']))
            return "000|status updated successfully|";
         else
            return "101|invalid merchant details or invalid response code|";

}


$server = new nusoap_server();


    $server->configureWSDL("UpdateOrderPaymentStatus6", "urn:UpdateOrderPaymentStatus6");
    $server->register(
        'DoUpdatePaymentStatus',
        [
            'pp_Version' => 'xsd:string',
            'pp_TxnType' => 'xsd:string',
            'pp_BankID' => 'xsd:string',
            'pp_Password' => 'xsd:string',
            'pp_TxnRefNo' => 'xsd:string',
            'pp_TxnDateTime' => 'xsd:string',
            'pp_ResponseCode' => 'xsd:string',
            'pp_ResponseMessage' => 'xsd:string',
            'pp_AuthCode' => 'xsd:string',
            'pp_RetreivalReferenceNo' => 'xsd:string',
            'pp_SecureHash' => 'xsd:string',
            'pp_ProductID' => 'xsd:string',
            'pp_SettlementExpiry' => 'xsd:string'
        ],
        ['DoUpdatePaymentStatusResult' => 'xsd:string']
    );




    $HTTP_RAW_POST_DATA =  file_get_contents("php://input");
    $server->service($HTTP_RAW_POST_DATA);

http://www.altijarahtrading.com/jazzCash/UpdateOrderPaymentStatus6.php?wsdl

<?php
$pp_version = '1.1';
$pp_TxnType='OTC';
$MerchantID = '00137171';//merchant id
$Password = '7w9377041a'; // password
$_TxnRefNumber = "TXN20171205073910";// Transaction Reference Number
$_TxnDateTime = "20171205073910"  ;//Time Function
$pp_ResponseCode="121"; // it will be 121 when jazz will call our api service
$pp_ResponseMessage="Order is placed and waiting for financials to be received over the counter";
$pp_RetreivalReferenceNo="1234";
$url  = `'http://www.altijarahtrading.com/jazzCash/UpdateOrderPaymentStatus6.php?wsdl';`
$client      = new SoapClient($url,array("trace" => 1, "exception" => 0));

$result=$client->DoUpdatePaymentStatus($pp_version ,
    $pp_TxnType,"",
    $Password,$_TxnRefNumber,$_TxnDateTime,
    $pp_ResponseCode,
    $pp_ResponseMessage
    ,"",
    $pp_RetreivalReferenceNo,
    "",
    "","","");

echo $result;
exit(0)
?>

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.InvalidOperationException: Client found response content type of 'text/html; charset=UTF-8', but expected 'text/xml'.