refactored http_conditionalRequest($timestamp) to inc/pageutils.php

darcs-hash:20060315064506-05dcb-92833a95f37a43ef50e6b993930ac9d25caed81f.gz

1 files changed, 36 insertions, 0 deletions

diff --git a/inc/pageutils.php b/inc/pageutils.php
index 2a07b5fe6..0689ff6fe 100644
--- a/inc/pageutils.php
+++ b/inc/pageutils.php
@@ -330,4 +330,40 @@ function isVisiblePage($id){
   return !isHiddenPage($id);
 }
 
+/**
+ * Checks and sets HTTP headers for conditional HTTP requests
+ *
+ * @author Simon Willison <swillison@gmail.com>
+ * @link   http://simon.incutio.com/archive/2003/04/23/conditionalGet
+ */
+function http_conditionalRequest($timestamp){
+    // A PHP implementation of conditional get, see 
+    //   http://fishbowl.pastiche.org/archives/001132.html
+    $last_modified = substr(date('r', $timestamp), 0, -5).'GMT';
+    $etag = '"'.md5($last_modified).'"';
+    // Send the headers
+    header("Last-Modified: $last_modified");
+    header("ETag: $etag");
+    // See if the client has provided the required headers
+    $if_modified_since = isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) ?
+        stripslashes($_SERVER['HTTP_IF_MODIFIED_SINCE']) :
+        false;
+    $if_none_match = isset($_SERVER['HTTP_IF_NONE_MATCH']) ?
+        stripslashes($_SERVER['HTTP_IF_NONE_MATCH']) : 
+        false;
+    if (!$if_modified_since && !$if_none_match) {
+        return;
+    }
+    // At least one of the headers is there - check them
+    if ($if_none_match && $if_none_match != $etag) {
+        return; // etag is there but doesn't match
+    }
+    if ($if_modified_since && $if_modified_since != $last_modified) {
+        return; // if-modified-since is there but doesn't match
+    }
+    // Nothing has changed since their last request - serve a 304 and exit
+    header('HTTP/1.0 304 Not Modified');
+    exit;
+}
+
 //Setup VIM: ex: et ts=2 enc=utf-8 :