session_start();

if(!isset($_SESSION['tos'])) {$_SESSION['tos'] == false;}

if($_GET['page'] != ("tos" || null)) {

  if($_SESSION['tos'] == false) { header("Location: index.php?page=tos");die();}

}

if($_POST["1"] == ("yes" || "Yes" || "YES" || "yEs" || "yeS" || "YEs" || "yES")) 
{
  header("Location: index.php?page=home");
  $_SESSION['tos'] = 1;
  die();
}