$_SERVER['HTTP_REFERER'] is always empty - PHP

<?php
$camefrom =$_SERVER['HTTP_REFERER'];
if ((substr($camefrom,0,26) == "http://www.fromperson.com")
header( 'Location: http://toperson.com' ) ;
?>

I need to redirect to www.to.com if the request was made from www.from.com. This code resides in www.thridperson.com/index.php

$camefrom is always empty.

I have read that $_SERVER['HTTP_REFERER'] is not reliable. Is there any other way to perform this redirection?

Note: I have lost the access to old domain i.e f开发者_开发知识库romperson.com. So, I cannot change this redirection logic it has to be done this way and it has to done only in thirdperson.com/index/php

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$_SERVER['HTTP_REFERER'] is indeed unreliable. A client (browser) is not required to include it in the request. If you need a bullet-proof solution that will always work you will have to moddiffy your application on `fromperson.com' to include some GET parameter when linking to your web page, and then you can check if that GET parameter exists and then do the redirect.

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No way to do according to my requirement