the page from which the user is visiting the current page

I have a web site with several pages. Page1, Page2, .. etc

I don't want the user to visit Pag开发者_开发问答e2 posting its URL directly in the browser because Page2 should be visited only from Page1. In PHP, what should I code in Page2 to know that the user was before in Page1 and clicked a link or something that brough him or her to Page2? Thanks.

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You could use

 $_SERVER['HTTP_REFERER']

though you can't rely on it being set every time.

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You could use PHP sessions.

page1.php

session_start();
$_SESSION['pages_visited'][basename(__FILE__)] = true;

page2.php

session_start();
$_SESSION['pages_visited'][basename(__FILE__)] = true;

if (!isset($_SESSION['pages_visited']['page1.php']) || !$_SESSION['pages_visited']['page1.php']) {
    header('Location: page1.php');
    exit;
}

---

In order to implement reliable mechanism, you may use sessions mechanism: http://www.php.net/manual/en/book.session.php

In this case information about visited pages can be stored on server side and will be retrieved by session id, which is stored in user's cookies / GET/POST variables