Index: includes/database/database.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/database/database.inc,v
retrieving revision 1.118
diff -u -r1.118 database.inc
--- includes/database/database.inc	23 Apr 2010 05:21:19 -0000	1.118
+++ includes/database/database.inc	23 Apr 2010 06:07:12 -0000
@@ -559,7 +559,7 @@
       }
     }
     catch (PDOException $e) {
-      _db_check_install_needed();
+      _drupal_check_install_needed();
       if ($options['throw_exception']) {
         // Add additional debug information.
         if ($query instanceof DatabaseStatementInterface) {
@@ -1408,7 +1408,7 @@
   final public static function parseConnectionInfo() {
     global $databases;
 
-    _db_check_install_needed();
+    _drupal_check_install_needed();
 
     $database_info = is_array($databases) ? $databases : array();
     foreach ($database_info as $index => $info) {
@@ -1533,7 +1533,7 @@
       // It is extremely rare that an exception will be generated here other
       // than when installing. We therefore intercept it and try the installer,
       // passing on the exception otherwise.
-      _db_check_install_needed();
+      _drupal_check_install_needed();
       throw $e;
     }
   }
@@ -2898,18 +2898,3 @@
     $_SESSION['ignore_slave_server'] = REQUEST_TIME + $duration;
   }
 }
-
-/**
- * Redirects the user to the installation script.
- *
- * This will check if Drupal has not been installed yet (i.e., if no $databases
- * array has been defined in the settings.php file) and we are not already
- * installing. If both are true, the user is redirected to install.php.
- */
-function _db_check_install_needed() {
-  global $databases;
-  if (empty($databases) && !drupal_installation_attempted()) {
-    include_once DRUPAL_ROOT . '/includes/install.inc';
-    install_goto('install.php');
-  }
-}
Index: includes/bootstrap.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/bootstrap.inc,v
retrieving revision 1.375
diff -u -r1.375 bootstrap.inc
--- includes/bootstrap.inc	23 Apr 2010 05:21:19 -0000	1.375
+++ includes/bootstrap.inc	23 Apr 2010 06:07:12 -0000
@@ -1955,6 +1955,12 @@
     header($_SERVER['SERVER_PROTOCOL'] . ' 403 Forbidden');
     exit;
   }
+
+  // Redirect to install.php if PDO is not installed.
+  if (!extension_loaded('pdo')) {
+    _drupal_check_install_needed();
+  }
+
   // Initialize the database system. Note that the connection
   // won't be initialized until it is actually requested.
   require_once DRUPAL_ROOT . '/includes/database/database.inc';
@@ -2733,3 +2739,18 @@
     }
   }
 }
+
+/**
+ * Redirects the user to the installation script.
+ *
+ * This will check if Drupal has not been installed yet (i.e., if no $databases
+ * array has been defined in the settings.php file) and we are not already
+ * installing. If both are true, the user is redirected to install.php.
+ */
+function _drupal_check_install_needed() {
+  global $databases;
+  if (empty($databases) && !drupal_installation_attempted()) {
+    include_once DRUPAL_ROOT . '/includes/install.inc';
+    install_goto('install.php');
+  }
+}
Index: includes/database/pgsql/database.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/database/pgsql/database.inc,v
retrieving revision 1.36
diff -u -r1.36 database.inc
--- includes/database/pgsql/database.inc	7 Mar 2010 08:03:45 -0000	1.36
+++ includes/database/pgsql/database.inc	23 Apr 2010 06:07:12 -0000
@@ -90,7 +90,7 @@
       }
     }
     catch (PDOException $e) {
-      _db_check_install_needed();
+      _drupal_check_install_needed();
       if ($options['throw_exception']) {
         // Add additional debug information.
         if ($query instanceof DatabaseStatementInterface) {