what does this file do?

[rezausa2010]

hello there so i have a script and i was just looking around it and i countered this file :
can someone explain what does it do? its kinda suspicious
thanks

<?phpinclude('GameEngine/Protection.php');$gvresult = 2;include('GameEngine/Database.php');echo 'GVResult:\n';$server = isset($_POST['server'])?$_POST['server']:'';$username = isset($_POST['username'])?$_POST['username']:'';$gold = isset($_POST['gold'])?intval($_POST['gold']):'';$ref = isset($_POST['ref'])?$_POST['ref']:'';if(strlen($server)>0 && strlen($username)>0 && $gold>0 && strlen($ref)>0){	$sig = SECSIG;	$myref = sha1($username.':sig'.$sig.':'.$server.'server:'.$gold);	if($myref==$ref){		$userData = $database->getUser($username);		if (!empty($userData)) {			$database->modifyUser($userData['id'],'gold',$userData['gold']+$gold,0);			$database->modifyUser($userData['id'],'transferedgold',$userData['transferedgold']+$gold,0);			$gvresult = 21;		} else {			$gvresult = 5;		}	} else {		$gvresult = 4;	}} else {	$gvresult = 3;}echo 'resultcode='.$gvresult.'\n';?>

 

[afterfx]

It has to do something with referral system, because the code

modifyUser($userData['id'],'gold',$userData['gold']+$gold,0);

; clearly updates users gold. Not 100% sure though.