[AndreT]

MyBB code:

PHP код:

function generate_salt()
{
    return random_str(8);
}
function salt_password($password, $salt)
{
    return md5(md5($salt).$password);
}

$pass = $mybb->input['password'];

$md5pass = md5($pass);
$salt = generate_salt();

$salted_pass = salt_password($md5pass, $salt); 


As you can see, $md5pass, which contains a MD5 hash, gets passed to the function salt_password.

So there's your mistake.