php - Make file only load if coming from specific url -

i have .php file , load if user coming specific page.

i.e. user must coming www.domain.com/main/index.php in order page www.domain.com/web/music/test.php load.

i have tried this:

<?php    $referrer = $_server['http_referer'];    if ($referrer != 'www.domain.com/main/index.php') {  die("this page can accessed www.domain.com/main/index.php.");   }    // put page code here   ?> 

but gives me error: notice: undefined index: http_referer.

any idea how this?

one way sessions, add session on every page.

page1.php:

<?php session_start(); $_session['prev_page'] = 'page1.php'; 

page2.php:

session_start(); if(isset($_session['prev_page']) && $_session['prev_page'] == 'page1.php'){   //your code here. }  $_session['prev_page'] = 'page2.php';