Different Variables Always Equal

[GreenKman]

So the idea is to check if it's empty (displays nothing), check if user "Bill" is sending a gift to him self (display $fail[1]), and if it gets past all of those checks, it should move on to the switch.
What seems to be happening is that $userid is always equal to $useridsender. Any ideas? D:

PHP Code:

$username=$_POST['username'];
$awardtype=$_POST['gift-type'];
$useridsender=$vbulletin->userinfo['userid'];
$uidlookup[query] ="SELECT * FROM vb_user WHERE username='$username'";
$uidlookup[result]= mysql_query($uidlookup[query]) or die(mysql_error());
while($row = mysql_fetch_array($uidlookup[result]))
{
    $userid=$row[userid];
}
$success[1] = "<b>Something shiny was successfully sent to</b> " . $username . ".";
$success[2] = "<b>Something traditional was successfully sent to</b> " . $username . ".";
$success[3] = "<b>Something colorful was successfully sent to</b> " . $username . ".";
$fail[1] = "<b>Sorry, you cannot send gifts to yourself. Please choose one of your friends.</b>";
if(empty($userid)){}
else{
        if($useridsender=$userid){
            echo $fail[1];
        }
        else{
            switch($awardtype){
                case 1:
                    echo $success[1];
                    break;
                case 2:
                    echo $success[2];
                    break;
                case 3:
                    echo $success[3];
                    break;
            }
        }
}