Problem with the database (MD5 HASH)...please help...

[jacks0_0]

I'm trying to integrate my system with vbulletin. In my file "signup.php" I had put this code:

$pass=md5(md5($_POST['password'].$salt));
$confirm=md5(md5($_POST['confirmpass'].$salt));

and then

$insertuser=mysql_query("insert into ".$tbfix."user (userid,fullname,username,password,email, permission,sex) values ('','$fullname','$username','$pass','$email','1',' $sex')") or die(mysql_error());
?>

And this is my code in my _function.php: (for login):

$sql=mysql_query("select permission,password,salt from ".$tbfix."user where userid='$cookieid'") or die(mysql_error());
$row=mysql_fetch_array($sql);
$salt=$row[salt];
$password=MD5(MD5($row[password].$salt));

it's working well when I register new member at my system (Vbulletin can read password and my system too) but when I register new member at vbulletin, only the vbb can read the password.

I have tried to figure out, and then I reg another member at my system, the password in the database is the same with the previous user and $salt has no effect :|

Please help me to solve this problem and tell me the easiest way to integrate a system with vbb ^ ^ thank you so much