Index: includes/bootstrap.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/bootstrap.inc,v
retrieving revision 1.220
diff -u -p -r1.220 bootstrap.inc
--- includes/bootstrap.inc	21 Aug 2008 19:36:36 -0000	1.220
+++ includes/bootstrap.inc	25 Aug 2008 07:26:06 -0000
@@ -1023,6 +1023,11 @@ function _drupal_bootstrap($phase) {
       break;
 
     case DRUPAL_BOOTSTRAP_DATABASE:
+      //Check if PDO is enabled.  If it is not then kill the script and point
+      //the user to the PHP website about PDO.
+      if (!class_exists('PDO')) {
+        die('<h2>PDO is required!</h2> Make sure your php configuration includes the PDO extension. <a href="http://www.php.net/pdo">Click here for more information on how to configure PDO.</a>');
+      }
       // Initialize the database system.  Note that the connection
       // won't be initialized until it is actually requested.
       require_once './includes/database/database.inc';