Windows what is wrong on my paygol script payment

[vBzone]

after payment not getting points tell me error
and this code of paygol.php
<?php

// get the variables from PayGol system
$message_id = $_GET['message_id'];
$service_id = $_GET['service_id'];
$shortcode = $_GET['shortcode'];
$keyword = $_GET['keyword'];
$message = $_GET['message'];
$sender = $_GET['sender'];
$operator = $_GET['operator'];
$country = $_GET['country'];
$custom = $_GET['custom'];
$points = $_GET['points'];
$price = $_GET['price'];
$currency = $_GET['currency'];

//Replace these parameters by your database details
$dbhost = "localhost"; //Your database domain
$dbuser = "root"; //Database username
$dbpassword = "hidden"; //Database password
$db = "hidden"; //Database name

//Connect to Database
$conn = mysql_connect($dbhost, $dbuser, $dbpassword);
mysql_select_db($db);

$sql = "UPDATE accounts SET premium_points = premium_points+$points WHERE name = '$custom'";
$result=mysql_query($sql);
if($result){
echo "Successful";
}

else {
echo "ERROR";
}
mysql_close($conn);

?>

i hope get help