It would be simpler as:
session_start();
$_SESSION['login']='yes';
$_SESSION['valid_user']=$entuser;
...
if($_SESSION['login'] != "yes")
{
print "You're not logged in";
} else {
print "You're logged in as $_SESSION[valid_user]";
From what I've seen on these forums, using session_register() is a sure road to madness...