Index: includes/bootstrap.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/bootstrap.inc,v
retrieving revision 1.304
diff -u -p -r1.304 bootstrap.inc
--- includes/bootstrap.inc	14 Sep 2009 07:43:11 -0000	1.304
+++ includes/bootstrap.inc	18 Sep 2009 16:36:55 -0000
@@ -848,7 +848,7 @@ function drupal_load($type, $name) {
  * @param $append
  *   Whether to append the value to an existing header or to replace it.
  */
-function drupal_set_header($name = NULL, $value = NULL, $append = FALSE) {
+function drupal_add_http_header($name = NULL, $value = NULL, $append = FALSE) {
   // The headers as name/value pairs.
   $headers = &drupal_static(__FUNCTION__, array());
 
@@ -890,8 +890,8 @@ function drupal_set_header($name = NULL,
  *   A string containing the header value, or FALSE if the header has been set,
  *   or NULL if the header has not been set.
  */
-function drupal_get_header($name = NULL) {
-  $headers = drupal_set_header();
+function drupal_get_http_header($name = NULL) {
+  $headers = drupal_add_http_header();
   if (isset($name)) {
     $name = strtolower($name);
     return isset($headers[$name]) ? $headers[$name] : NULL;
@@ -915,9 +915,9 @@ function _drupal_set_preferred_header_na
 }
 
 /**
- * Send the HTTP response headers previously set using drupal_set_header().
+ * Send the HTTP response headers previously set using drupal_add_http_header().
  * Add default headers, unless they have been replaced or unset using
- * drupal_set_header().
+ * drupal_add_http_header().
  *
  * @param $default_headers
  *   An array of headers as name/value pairs.
@@ -926,7 +926,7 @@ function _drupal_set_preferred_header_na
  */
 function drupal_send_headers($default_headers = array(), $only_default = FALSE) {
   $headers_sent = &drupal_static(__FUNCTION__, FALSE);
-  $headers = drupal_get_header();
+  $headers = drupal_get_http_header();
   if ($only_default && $headers_sent) {
     $headers = array();
   }
@@ -999,7 +999,7 @@ function drupal_page_header() {
  *
  * The headers allow as much as possible in proxies and browsers without any
  * particular knowledge about the pages. Modules can override these headers
- * using drupal_set_header().
+ * using drupal_add_http_header().
  *
  * If the request is conditional (using If-Modified-Since and If-None-Match),
  * and the conditions match those currently in the cache, a 304 Not Modified
@@ -1011,10 +1011,10 @@ function drupal_serve_page_from_cache(st
   $return_compressed = $page_compression && isset($_SERVER['HTTP_ACCEPT_ENCODING']) && strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== FALSE;
 
   // Get headers set in hook_boot(). Keys are lower-case.
-  $hook_boot_headers = drupal_get_header();
+  $hook_boot_headers = drupal_get_http_header();
 
   // Headers generated in this function, that may be replaced or unset using
-  // drupal_set_headers(). Keys are mixed-case.
+  // drupal_add_http_headers(). Keys are mixed-case.
   $default_headers = array();
 
   foreach ($cache->headers as $name => $value) {
@@ -1023,7 +1023,7 @@ function drupal_serve_page_from_cache(st
     // headers set in hook_boot().
     $name_lower = strtolower($name);
     if (in_array($name_lower, array('content-location', 'expires', 'cache-control', 'vary')) && !isset($hook_boot_headers[$name_lower])) {
-      drupal_set_header($name, $value);
+      drupal_add_http_header($name, $value);
       unset($cache->headers[$name]);
     }
   }
@@ -1055,7 +1055,7 @@ function drupal_serve_page_from_cache(st
 
   // Send the remaining headers.
   foreach ($cache->headers as $name => $value) {
-    drupal_set_header($name, $value);
+    drupal_add_http_header($name, $value);
   }
 
   $default_headers['Last-Modified'] = gmdate(DATE_RFC1123, $cache->created);
Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.992
diff -u -p -r1.992 common.inc
--- includes/common.inc	18 Sep 2009 10:54:20 -0000	1.992
+++ includes/common.inc	18 Sep 2009 16:36:55 -0000
@@ -456,7 +456,7 @@ function drupal_goto($path = '', $query 
  */
 function drupal_site_offline() {
   drupal_maintenance_theme();
-  drupal_set_header('503 Service unavailable');
+  drupal_add_http_header('503 Service unavailable');
   drupal_set_title(t('Site under maintenance'));
   print theme('maintenance_page', filter_xss_admin(variable_get('maintenance_mode_message',
     t('@site is currently under maintenance. We should be back shortly. Thank you for your patience.', array('@site' => variable_get('site_name', 'Drupal'))))));
@@ -466,7 +466,7 @@ function drupal_site_offline() {
  * Generates a 404 error if the request can not be handled.
  */
 function drupal_not_found() {
-  drupal_set_header('404 Not Found');
+  drupal_add_http_header('404 Not Found');
 
   watchdog('page not found', check_plain($_GET['q']), NULL, WATCHDOG_WARNING);
 
@@ -498,7 +498,7 @@ function drupal_not_found() {
  * Generates a 403 error if the request is not allowed.
  */
 function drupal_access_denied() {
-  drupal_set_header('403 Forbidden');
+  drupal_add_http_header('403 Forbidden');
   watchdog('access denied', check_plain($_GET['q']), NULL, WATCHDOG_WARNING);
 
   // Keep old path for reference, and to allow forms to redirect to it.
@@ -950,7 +950,7 @@ function _drupal_log_error($error, $fata
   }
 
   if ($fatal) {
-    drupal_set_header('500 Service unavailable (with message)');
+    drupal_add_http_header('500 Service unavailable (with message)');
   }
 
   if (isset($_SERVER['HTTP_X_REQUESTED_WITH']) && $_SERVER['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest') {
@@ -3224,7 +3224,7 @@ function drupal_get_js($scope = 'header'
  * callback function and each value an array of arguments. For example:
  *
  * @code
- * $build['#attached']['drupal_set_header'] = array(
+ * $build['#attached']['drupal_add_http_header'] = array(
  *   array('Content-Type', 'application/rss+xml; charset=utf-8'),
  * );
  * @endcode
@@ -3602,7 +3602,7 @@ function drupal_to_js($var) {
  */
 function drupal_json($var = NULL) {
   // We are returning JavaScript, so tell the browser.
-  drupal_set_header('Content-Type', 'text/javascript; charset=utf-8');
+  drupal_add_http_header('Content-Type', 'text/javascript; charset=utf-8');
 
   if (isset($var)) {
     echo drupal_to_js($var);
@@ -3747,7 +3747,7 @@ function _drupal_bootstrap_full() {
   set_exception_handler('_drupal_exception_handler');
 
   // Emit the correct charset HTTP header.
-  drupal_set_header('Content-Type', 'text/html; charset=utf-8');
+  drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
   // Detect string handling method
   unicode_check();
   // Undo magic quotes
@@ -3799,9 +3799,9 @@ function drupal_page_set_cache() {
     );
 
     // Restore preferred header names based on the lower-case names returned
-    // by drupal_get_header().
+    // by drupal_get_http_header().
     $header_names = _drupal_set_preferred_header_name();
-    foreach (drupal_get_header() as $name_lower => $value) {
+    foreach (drupal_get_http_header() as $name_lower => $value) {
       $cache->headers[$header_names[$name_lower]] = $value;
     }
 
Index: includes/file.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/file.inc,v
retrieving revision 1.190
diff -u -p -r1.190 file.inc
--- includes/file.inc	31 Aug 2009 05:47:33 -0000	1.190
+++ includes/file.inc	18 Sep 2009 16:36:55 -0000
@@ -1502,7 +1502,7 @@ function file_transfer($uri, $headers) {
   }
 
   foreach ($headers as $name => $value) {
-    drupal_set_header($name, $value);
+    drupal_add_http_header($name, $value);
   }
   drupal_send_headers();
   $scheme = file_uri_scheme($uri);
Index: includes/theme.maintenance.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/theme.maintenance.inc,v
retrieving revision 1.40
diff -u -p -r1.40 theme.maintenance.inc
--- includes/theme.maintenance.inc	11 Sep 2009 13:56:56 -0000	1.40
+++ includes/theme.maintenance.inc	18 Sep 2009 16:36:55 -0000
@@ -119,7 +119,7 @@ function theme_task_list($items, $active
  *   The page content to show.
  */
 function theme_install_page($content) {
-  drupal_set_header('Content-Type', 'text/html; charset=utf-8');
+  drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
 
   // Assign content.
   $variables['content'] = $content;
@@ -176,7 +176,7 @@ function theme_install_page($content) {
  */
 function theme_update_page($content, $show_messages = TRUE) {
   // Set required headers.
-  drupal_set_header('Content-Type', 'text/html; charset=utf-8');
+  drupal_add_http_header('Content-Type', 'text/html; charset=utf-8');
 
   // Assign content and show message flag.
   $variables['content'] = $content;
Index: includes/xmlrpcs.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/xmlrpcs.inc,v
retrieving revision 1.31
diff -u -p -r1.31 xmlrpcs.inc
--- includes/xmlrpcs.inc	24 Aug 2009 00:14:19 -0000	1.31
+++ includes/xmlrpcs.inc	18 Sep 2009 16:36:55 -0000
@@ -106,8 +106,8 @@ function xmlrpc_server_error($error, $me
 
 function xmlrpc_server_output($xml) {
   $xml = '<?xml version="1.0"?>' . "\n" . $xml;
-  drupal_set_header('Content-Length', strlen($xml));
-  drupal_set_header('Content-Type', 'text/xml');
+  drupal_add_http_header('Content-Length', strlen($xml));
+  drupal_add_http_header('Content-Type', 'text/xml');
   echo $xml;
   exit;
 }
Index: includes/database/database.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/database/database.inc,v
retrieving revision 1.76
diff -u -p -r1.76 database.inc
--- includes/database/database.inc	18 Sep 2009 00:04:21 -0000	1.76
+++ includes/database/database.inc	18 Sep 2009 16:36:55 -0000
@@ -2426,7 +2426,7 @@ function _db_error_page($error = '') {
   global $db_type;
   drupal_language_initialize();
   drupal_maintenance_theme();
-  drupal_set_header($_SERVER['SERVER_PROTOCOL'] . ' 503 Service Unavailable');
+  drupal_add_http_header($_SERVER['SERVER_PROTOCOL'] . ' 503 Service Unavailable');
   drupal_set_title('Site offline');
 }
 
Index: modules/aggregator/aggregator.pages.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/aggregator/aggregator.pages.inc,v
retrieving revision 1.33
diff -u -p -r1.33 aggregator.pages.inc
--- modules/aggregator/aggregator.pages.inc	18 Sep 2009 00:04:22 -0000	1.33
+++ modules/aggregator/aggregator.pages.inc	18 Sep 2009 16:36:55 -0000
@@ -369,7 +369,7 @@ function aggregator_page_rss() {
  * @ingroup themeable
  */
 function theme_aggregator_page_rss($feeds, $category = NULL) {
-  drupal_set_header('Content-Type', 'application/rss+xml; charset=utf-8');
+  drupal_add_http_header('Content-Type', 'application/rss+xml; charset=utf-8');
 
   $items = '';
   $feed_length = variable_get('feed_item_length', 'teaser');
@@ -429,7 +429,7 @@ function aggregator_page_opml($cid = NUL
  * @ingroup themeable
  */
 function theme_aggregator_page_opml($feeds) {
-  drupal_set_header('Content-Type', 'text/xml; charset=utf-8');
+  drupal_add_http_header('Content-Type', 'text/xml; charset=utf-8');
 
   $output  = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n";
   $output .= "<opml version=\"1.1\">\n";
Index: modules/aggregator/tests/aggregator_test.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/aggregator/tests/aggregator_test.module,v
retrieving revision 1.3
diff -u -p -r1.3 aggregator_test.module
--- modules/aggregator/tests/aggregator_test.module	27 May 2009 18:33:54 -0000	1.3
+++ modules/aggregator/tests/aggregator_test.module	18 Sep 2009 16:36:55 -0000
@@ -33,21 +33,21 @@ function aggregator_test_feed($use_last_
   // Send appropriate response. We respond with a 304 not modified on either
   // etag or on last modified.
   if ($use_last_modified) {
-    drupal_set_header('Last-Modified', gmdate(DATE_RFC1123, $last_modified));
+    drupal_add_http_header('Last-Modified', gmdate(DATE_RFC1123, $last_modified));
   }
   if ($use_etag) {
-    drupal_set_header('ETag', $etag);
+    drupal_add_http_header('ETag', $etag);
   }
   // Return 304 not modified if either last modified or etag match.
   if ($last_modified == $if_modified_since || $etag == $if_none_match) {
-    drupal_set_header('304 Not Modified');
+    drupal_add_http_header('304 Not Modified');
     return;
   }
 
   // The following headers force validation of cache:
-  drupal_set_header('Expires', 'Sun, 19 Nov 1978 05:00:00 GMT');
-  drupal_set_header('Cache-Control', 'must-revalidate');
-  drupal_set_header('Content-Type', 'application/rss+xml; charset=utf-8');
+  drupal_add_http_header('Expires', 'Sun, 19 Nov 1978 05:00:00 GMT');
+  drupal_add_http_header('Cache-Control', 'must-revalidate');
+  drupal_add_http_header('Content-Type', 'application/rss+xml; charset=utf-8');
 
   // Read actual feed from file.
   $file_name = DRUPAL_ROOT . '/' . drupal_get_path('module', 'aggregator') . '/tests/aggregator_test_rss091.xml';
Index: modules/image/image.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/image/image.module,v
retrieving revision 1.16
diff -u -p -r1.16 image.module
--- modules/image/image.module	26 Aug 2009 03:20:39 -0000	1.16
+++ modules/image/image.module	18 Sep 2009 16:36:55 -0000
@@ -453,8 +453,8 @@ function image_style_generate() {
     if (!$lock_acquired) {
       // Tell client to retry again in 3 seconds. Currently no browsers are known
       // to support Retry-After.
-      drupal_set_header('503 Service Unavailable');
-      drupal_set_header('Retry-After', 3);
+      drupal_add_http_header('503 Service Unavailable');
+      drupal_add_http_header('Retry-After', 3);
       print t('Image generation in progress, please try again shortly.');
       exit();
     }
@@ -474,7 +474,7 @@ function image_style_generate() {
   }
   else {
     watchdog('image', 'Unable to generate the derived image located at %path.', $destination);
-    drupal_set_header('500 Internal Server Error');
+    drupal_add_http_header('500 Internal Server Error');
     print t('Error generating image.');
     exit();
   }
Index: modules/node/node.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/node/node.module,v
retrieving revision 1.1126
diff -u -p -r1.1126 node.module
--- modules/node/node.module	18 Sep 2009 00:12:47 -0000	1.1126
+++ modules/node/node.module	18 Sep 2009 16:37:18 -0000
@@ -1872,7 +1872,7 @@ function node_feed($nids = FALSE, $chann
   $output .= format_rss_channel($channel['title'], $channel['link'], $channel['description'], $items, $channel['language']);
   $output .= "</rss>\n";
 
-  drupal_set_header('Content-Type', 'application/rss+xml; charset=utf-8');
+  drupal_add_http_header('Content-Type', 'application/rss+xml; charset=utf-8');
   print $output;
 }
 
Index: modules/openid/tests/openid_test.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/openid/tests/openid_test.module,v
retrieving revision 1.3
diff -u -p -r1.3 openid_test.module
--- modules/openid/tests/openid_test.module	10 Jun 2009 20:13:20 -0000	1.3
+++ modules/openid/tests/openid_test.module	18 Sep 2009 16:36:55 -0000
@@ -69,7 +69,7 @@ function openid_test_menu() {
  */
 function openid_test_yadis_xrds() {
   if ($_SERVER['HTTP_ACCEPT'] == 'application/xrds+xml') {
-    drupal_set_header('Content-Type', 'application/xrds+xml');
+    drupal_add_http_header('Content-Type', 'application/xrds+xml');
     print '<?xml version="1.0" encoding="UTF-8"?>
       <xrds:XRDS xmlns:xrds="xri://$xrds" xmlns="xri://$xrd*($v*2.0)">
         <XRD>
@@ -89,7 +89,7 @@ function openid_test_yadis_xrds() {
  * Menu callback; regular HTML page with an X-XRDS-Location HTTP header.
  */
 function openid_test_yadis_x_xrds_location() {
-  drupal_set_header('X-XRDS-Location', url('openid-test/yadis/xrds', array('absolute' => TRUE)));
+  drupal_add_http_header('X-XRDS-Location', url('openid-test/yadis/xrds', array('absolute' => TRUE)));
   return t('This page includes an X-RDS-Location HTTP header containing the URL of an XRDS document.');
 }
 
@@ -181,7 +181,7 @@ function _openid_test_endpoint_associate
 
   // Respond to Relying Party in the special Key-Value Form Encoding (see OpenID
   // Authentication 1.0, section 4.1.1).
-  drupal_set_header('Content-Type', 'text/plain');
+  drupal_add_http_header('Content-Type', 'text/plain');
   print _openid_create_message($response);
 }
 
@@ -228,6 +228,6 @@ function _openid_test_endpoint_authentic
 
   // Put the signed message into the query string of a URL supplied by the
   // Relying Party, and redirect the user.
-  drupal_set_header('Content-Type', 'text/plain');
+  drupal_add_http_header('Content-Type', 'text/plain');
   header('Location: ' . url($_REQUEST['openid_return_to'], array('query' => http_build_query($response, '', '&'), 'external' => TRUE)));
 }
Index: modules/simpletest/tests/browser_test.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/browser_test.module,v
retrieving revision 1.2
diff -u -p -r1.2 browser_test.module
--- modules/simpletest/tests/browser_test.module	18 Sep 2009 00:12:47 -0000	1.2
+++ modules/simpletest/tests/browser_test.module	18 Sep 2009 16:36:55 -0000
@@ -69,7 +69,7 @@ function browser_test_refresh_meta() {
 function browser_test_refresh_header() {
   if (!isset($_GET['refresh'])) {
     $url = url('browser_test/refresh/header', array('absolute' => TRUE, 'query' => 'refresh=true'));
-    drupal_set_header('Location', $url);
+    drupal_add_http_header('Location', $url);
     return '';
   }
   echo 'Refresh successful';
Index: modules/simpletest/tests/system_test.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/system_test.module,v
retrieving revision 1.15
diff -u -p -r1.15 system_test.module
--- modules/simpletest/tests/system_test.module	17 Aug 2009 20:32:30 -0000	1.15
+++ modules/simpletest/tests/system_test.module	18 Sep 2009 16:36:55 -0000
@@ -96,7 +96,7 @@ function system_test_redirect($code) {
 }
 
 function system_test_set_header() {
-  drupal_set_header($_GET['name'], $_GET['value']);
+  drupal_add_http_header($_GET['name'], $_GET['value']);
   return t('The following header was set: %name: %value', array('%name' => $_GET['name'], '%value' => $_GET['value']));
 }
 
Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.791
diff -u -p -r1.791 system.module
--- modules/system/system.module	18 Sep 2009 00:12:48 -0000	1.791
+++ modules/system/system.module	18 Sep 2009 16:36:55 -0000
@@ -3001,7 +3001,7 @@ function theme_meta_generator_html($vers
  * @ingroup themeable
  */
 function theme_meta_generator_header($version = VERSION) {
-  drupal_set_header('X-Generator', 'Drupal ' . $version . ' (http://drupal.org)');
+  drupal_add_http_header('X-Generator', 'Drupal ' . $version . ' (http://drupal.org)');
 }
 
 /**
@@ -3095,7 +3095,7 @@ function system_run_cron_image() {
 
   // Output a transparent 1x1 image to the browser; required for clients not
   // supporting JavaScript.
-  drupal_set_header('Content-Type', 'image/gif');
+  drupal_add_http_header('Content-Type', 'image/gif');
   echo "\x47\x49\x46\x38\x39\x61\x1\x0\x1\x0\x80\xff\x0\xc0\xc0\xc0\x0\x0\x0\x21\xf9\x4\x1\x0\x0\x0\x0\x2c\x0\x0\x0\x0\x1\x0\x1\x0\x0\x2\x2\x44\x1\x0\x3b";
 
   // Cron threshold semaphore is used to avoid errors every time the image