preventing direct access to a php page, only access if redirected

Question

I want to make my php page only accessible from another page redirect and prevent my user from accessing it directly.

I mean, let\'s say I have a page called

Answer 1

You can use $_SERVER["HTTP_REFERER"]. Put the following code in the beginning of your php file and set $url to be equal of your desired url for example http://a.com/main.php

if ($_SERVER['HTTP_REFERER'] != $url) {
    header('Location: noaccess.php');
    exit();
}