Csrf prevention

What is A cross Site Request Forgery?

CSRF Cross-Site Request Forgery Atack: Embed an image in some arbitrary Web site
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If it happend that you are logged on and you browse, you'll make a purchase, even if you don't want to. The token method involves the use of a randomly generated token that is stored in the user's session when the user accesses the form page and is also placed in a hidden field on the form. <?php session_start(); if (isset($_POST['btn_submit'])) { if (isset($_SESSION['token']) && isset($_POST['token']) && $_POST['token'] == $_SESSION['token']) { echo 'Accepted'; } else { echo 'Denied'; } } $token = md5(uniqid(rand(), TRUE)); $_SESSION['token'] = $token; ?> <form method="POST"> <input type="hidden" name="token" value="<?php echo $token; ?>" /> <input type="submit" name="btn_submit"/> </form>