if (!isset($_SESSION['userid'])) {
  print "<form 'action = $PHP_SELF' 'method = POST'><br>";
  print "user: <input type=text name='userid'><br>";
  print "pass: <input type=text        name='id'><br>";
  print "<input type=submit name='submit' value='submit'><br>";
}
//elseif (!empty($_POST)) {
//  $_SESSION['userid'] = $_POST['userid'];
//  $_SESSION['id'] = $_POST['id'];
//  print "foo";
//}
else {
  print "You are logged in: " . print_r($_SESSION, TRUE);
}