Custom PHP processing page

Question

I have a PHP page already written specifically for users to be directed to (sort of like a referrer link, and carries querystring values) from external sites. This page is not intended to have any theming or Drupal content, and only is supposed to show a a single block of text in the middle-center of page with the words PROCESSING.... The intended workflow here is as follows:

1. User clicks on a link from an affiliate-type site that links to something along the lines of www.example.com?reciprocate.php?a=x&b=y&c=z in my Drupal website.
2. reciprocate.php then checks if the user is currently logged in, and if not, presents the user with the Drupal login form, and preserves the querystring values in a post variable, and posts back to itself.
3. If the user is logged in, then the page will fetch some data from an external source, process it along with the original querystring values.
4. Depending on the results of the processing, the user will then be redirected to an appropriate URL (for authenticated users only) within the site.

I can't seem to find any way to do this with either Drupal core or contrib modules, and I know I should be creating a custom module to do this, but I honestly haven't got around to learning how to do that, but believe me I will soon! Therefore hopefully you will understand the approach I took...I know it's not great, but I'm trying to work with what little I know.

I've already created my page at the root of my site, with all of my processing code, but I just can't seem to access any Drupal globals using the following as a test:

<?php
    include("includes\bootstrap.inc");
    drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);
    global $user;
    if ($user->uid) {
       // do custom processing here
    } else {
       print drupal_get_form('user_login_block');
    }
?>

Please see if there is any way you can assist me, as I am really desperate. This may seem like a simple isolated block of code, but my site really relies on it. I thank you most humbly in advance!

Answer 1

Your code should be similar to the index.php file that comes with Drupal, at least for the part that bootstraps Drupal.

define('DRUPAL_ROOT', getcwd());

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

if (user_is_logged_in()) {
  // do custom processing here
}
else {
  drupal_render(drupal_get_form('user_login_block'));
}

Drupal code requires the DRUPAL_ROOT constant to be defined, as that constant is used to include PHP files.

    case DRUPAL_BOOTSTRAP_SESSION:
      require_once DRUPAL_ROOT . '/' . variable_get('session_inc', 'includes/session.inc');
      drupal_session_initialize();
      break;

If you look at the errors in the server log, it is probable you will find some errors about the constant not being defined, or about files not being found by require_once.

I am assuming you copied your PHP file in the same directory that contains index.php, and update.php that comes with Drupal.
Otherwise, the generic code to bootstrap Drupal from an external PHP file is the following one, suggested in drupal_bootstrap() documentation.

define('DRUPAL_ROOT', '/path/to/drupal');
require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

Replace 'path/to/drupal' with the absolute path where the Drupal files are copied.

Instead of trying to render a specific form, I would rather redirect the users to the page containing the login form. This method allows you to set the destination of the login form, which where the users are redirected after they submitted the login form.

define('DRUPAL_ROOT', getcwd());

require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

if (user_is_logged_in()) {
  // do custom processing here
}
else {
  // The following line is probably not necessary, but if the user access the page
  // with reciprocate.php?destination=anotherpage, s/he will be redirected to anotherpage.
  unset($_GET['destination']);

  drupal_goto('user/login', array('query' => array('destination' => str_replace('%2F', '/', rawurlencode('reciprocate.php?a=x&b=y&c=z')))));
}

With Drupal 8, the code to fully bootstrap Drupal is slightly different.

define('DRUPAL_ROOT', getcwd());

require_once DRUPAL_ROOT . '/core/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

define('DRUPAL_ROOT', '/path/to/drupal');
require_once DRUPAL_ROOT . '/core/includes/bootstrap.inc';
drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);

The difference is the name of the directory containing the core files.

Answer 2

SOLVED!!...I think :)

I decided to give the "Login Destination" module one last shot.

1. Created a rule for reciprocate as its own destination under Login Destination configuration.
2. Created a Page node, gave it some arbitrary title, and gave it a URL alias of reciprocate. This was associated as Node-10 in Drupal.
3. In my theme, I cloned node.tpl.php and renamed it to node--10.tpl.php.
4. In this file I wiped everything and added my code from my original post above, starting from global $user;... (omitting the DRUPAL_ROOT definition bit).
5. Browsed to my new page (unauthenticated) and included some test querystring values: http://localhost/kindred.test/reciprocate?a=x&b=y&c=z
6. Was presented with a login block, and after logging in, I was redirected back to /reciprocate with my querystring values intact!!
7. My // do custom processing here ran successfully, and as a test pulled in my querystring values using $_GET

I'm really chuffed that worked out! took my entire weekend, but worth it in the end. Thank you though to kiamlaluno for your help and patience.