Redirecting anonymous users to the login page on Access Denied

This shows how to redirect anonymous users to a sign up/login page when they came across access denied (error 403) pages by using a PHP page. You may also want to check the LoginToboggan module as well for another solution.

Process

1. Create a node of type page. You must have the PHP input filter enabled.
2. In the body of the page insert:
   
   <?php
global $user;
if ($user->uid) { // this user is already logged in
print "Access Denied: You do not have access to this page.";
} else {
drupal_set_message("Access Denied: Please Login");
$dest = drupal_get_destination();
drupal_goto('user/login', $dest); // this remembers where the user is coming from
}
?>
3. Submit the node (you should see the "Access Denied: You do not have access to this page." message
4. Remember this node's ID number
5. Goto admin/settings
6. In the section about alternate 403 error pages, insert "node/XXXX" where XXX is your node's ID number
7. Test it

If you would prefer, you can use this alternate code to force a redirect to the login page after 10 seconds (instead of immediately).