php - 不会根据iframe中的referrer父URL重定向

I have a page with an iframe with the following code. Basically I want it to act like a portal. Depending on which page they're visiting this from, they will see a different thing. When I tried to get the referrer with echo, it managed to fetch the parent URL but wouldn't redirect properly. Instead it would go to the default. I was wondering if this is something that is impossible to do?

$referrer = $_SERVER['HTTP_REFERER'];

switch($referrer) {
   case "https://domain1.org":
      header("Location: https://example.org/one");
      break;
   case "http://domain2.org");
      header("Location: https://example.org/two");
      break;
   case "https://domain3.org":
      header("Location: https://example.org/three");
      break;
   default:
      header("Location: https://example.org");
}

EDIT 1: It would only redirect to the case header if I change it to the iframe URL, not the parent. Otherwise it would redirect to the default header.

EDIT 2: I've set up a testing environment here. The problem persists.

Adding a variable to the iframe URL so that it would detect the given variable rather than the parent URL. Not what I had in mind but works well as an alternative in my case.

<iframe src="https://example.org/redirect.php?variable=redirect1"></iframe>

$var = $_GET['variable'];

switch($var) {
   case "redirect1":
      header("Location: https://example.org/one");
      break;
   case "redirect2";
      header("Location: https://example.org/two");
      break;
   case "redirect3":
      header("Location: https://example.org/three");
      break;
   default:
      header("Location: https://example.org");
}