You can save it to cookie or session and use it on the next page.
if (!isset($_SESSION)) {
session_start();
}
if (!isset($_SESSION['referrer'])) {
$_SESSION['referrer'] = isset($_SERVER['HTTP_REFERER']) ? $_SERVER['HTTP_REFERER'] : 'n/a';
}
// another page
$referer = isset($_SESSION['referrer']) ? $_SESSION['referrer'] : null;