Fix legacy IPN endpoint for Drupal (gitlab issue 973)

extern/ipn.php

@@ -29,6 +29,29 @@
  * @package CRM
  * @copyright CiviCRM LLC (c) 2004-2019
  * $Id$
+ *
+ * This script processes "Instant Payment Notifications" (IPNs).  Modern
+ * Payment Processors use the /civicrm/payment/ipn/123 endpoint instead (where
+ * 123 is the payment processor ID), however a quirk in the way PayPal works
+ * means that we need to maintain this script.
+ *
+ * Note on PayPal.
+ *
+ * Using PayPal Website Standard (which uses the old PayPal button API) the IPN
+ * endpoint is passed to PayPal with every transaction, and it is then stored
+ * by PayPal who unhelpfully do not give you any way to retrieve or change
+ * this.
+ *
+ * This means that if you provide URL1 when setting up a recurring
+ * contribution, then you will always need to maintain URL1 because all
+ * recurring payments against that will be sent to URL1.
+ *
+ * Note that this also affects you if you were to move your CiviCRM instance to
+ * another domain (if you do, get the webserver at the original domain to emit
+ * a 307 redirect to the new one, PayPal will re-send).
+ *
+ * Therefore, for the sake of these old recurring contributions, CiviCRM should
+ * maintain this script as part of core.
  */
 
 if (defined('PANTHEON_ENVIRONMENT')) {
@@ -53,8 +76,16 @@
 }
 try {
   //CRM-18245
-  if ($config->userFramework == 'Joomla') {
+  switch ($config->userFramework) {
+  case 'Joomla':
     CRM_Utils_System::loadBootStrap();
+    break;
+
+  case 'Drupal':
+    // Gitlab issue: #973
+    CRM_Utils_System::loadBootStrap([], FALSE);
+    break;
+
   }
   $paypalIPN->main();
 }