diff --git a/wp-blog-header.php b/wp-blog-header.php
index 9d5f3711b0..d6f83a1db3 100644
--- a/wp-blog-header.php
+++ b/wp-blog-header.php
@@ -10,16 +10,60 @@ if (!file_exists($curpath . '/wp-config.php'))
 
 require($curpath.'/wp-config.php');
 
+/* Process PATH_INFO, if set. */
+$path_info = array();
+if (! empty($_SERVER['PATH_INFO'])) {
+    // Fetch the rewrite rules.
+    $rewrite = rewrite_rules('matches');
+
+    $pathinfo = $_SERVER['PATH_INFO'];
+    // Trim leading '/'.
+    $pathinfo = preg_replace("!^/!", '', $pathinfo);
+
+    if (! empty($rewrite)) {
+        // Get the name of the file requesting path info.
+        $req_uri = $HTTP_SERVER_VARS['REQUEST_URI'];
+        $req_uri = str_replace($pathinfo, '', $req_uri);
+        $req_uri = preg_replace("!/+$!", '', $req_uri);
+        $req_uri = explode('/', $req_uri);
+        $req_uri = $req_uri[count($req_uri)-1];
+
+        // Look for matches.
+        $pathinfomatch = $pathinfo;
+        foreach ($rewrite as $match => $query) {
+            // If the request URI is the anchor of the match, prepend it
+            // to the path info.
+            if (preg_match("!^$req_uri!", $match)) {
+                $pathinfomatch = $req_uri . '/' . $pathinfo;
+            }
+
+            if (preg_match("!^$match!", $pathinfomatch, $matches)) {
+                // Got a match.
+                // Trim the query of everything up to the '?'.
+                $query = preg_replace("!^.+\?!", '', $query);
+
+                // Substitute the substring matches into the query.
+                eval("\$query = \"$query\";");
+
+                // Parse the query.
+                parse_str($query, $path_info);
+            }
+        }
+    }    
+}
+
 $wpvarstoreset = array('m','p','posts','w', 'cat','withcomments','s','search','exact', 'sentence','poststart','postend','preview','debug', 'calendar','page','paged','more','tb', 'pb','author','order','orderby', 'year', 'monthnum', 'day', 'name', 'category_name', 'feed', 'author_name');
 
     for ($i=0; $i<count($wpvarstoreset); $i += 1) {
         $wpvar = $wpvarstoreset[$i];
         if (!isset($$wpvar)) {
             if (empty($HTTP_POST_VARS[$wpvar])) {
-                if (empty($HTTP_GET_VARS[$wpvar])) {
+                if (empty($HTTP_GET_VARS[$wpvar]) && empty($path_info[$wpvar])) {
                     $$wpvar = '';
-                } else {
+                } elseif (!empty($HTTP_GET_VARS[$wpvar])) {
                     $$wpvar = $HTTP_GET_VARS[$wpvar];
+                } else {
+                    $$wpvar = $path_info[$wpvar];
                 }
             } else {
                 $$wpvar = $HTTP_POST_VARS[$wpvar];
diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index c875b48d34..b4069fc859 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -1330,4 +1330,141 @@ function hilite($text) {
 	return $text;
 }
 
-?>
\ No newline at end of file
+/* rewrite_rules
+ * Construct rewrite matches and queries from permalink structure.
+ * matches - The name of the match array to use in the query strings.
+ *           If empty, $1, $2, $3, etc. are used.
+ * Returns an associate array of matches and queries.
+ */
+function rewrite_rules($matches = '') {
+
+    function preg_index($number, $matches = '') {
+        $match_prefix = '$';
+        $match_suffix = '';
+        
+        if (! empty($matches)) {
+            $match_prefix = '$' . $matches . '['; 
+                                               $match_suffix = ']';
+        }        
+        
+        return "$match_prefix$number$match_suffix";        
+    }
+    
+    $rewrite = array();
+
+    $permalink_structure = get_settings('permalink_structure');
+
+    if (empty($permalink_structure)) {
+        return $rewrite;
+    }
+
+    $rewritecode = array(
+                         '%year%',
+                         '%monthnum%',
+                         '%day%',
+                         '%postname%',
+                         '%post_id%'
+                         );
+
+    $rewritereplace = array(
+                            '([0-9]{4})?',
+                            '([0-9]{1,2})?',
+                            '([0-9]{1,2})?',
+                            '([0-9a-z-]+)?',
+                            '([0-9]+)?'
+                            );
+
+    $queryreplace = array (
+                           'year=',
+                           'monthnum=',
+                           'day=',
+                           'name=',
+                           'p='
+                           );
+
+
+    $match = str_replace('/', '/?', $permalink_structure);
+    $match = preg_replace('|/[?]|', '', $match, 1);
+
+    $match = str_replace($rewritecode, $rewritereplace, $match);
+    $match = preg_replace('|[?]|', '', $match, 1);
+
+    $feedmatch = str_replace('?/?', '/', $match);
+    $trackbackmatch = $feedmatch;
+
+    preg_match_all('/%.+?%/', $permalink_structure, $tokens);
+
+    $query = 'index.php?';
+    $feedquery = 'wp-feed.php?';
+    $trackbackquery = 'wp-trackback.php?';
+    for ($i = 0; $i < count($tokens[0]); ++$i) {
+             if (0 < $i) {
+                 $query .= '&';
+                 $feedquery .= '&';
+                 $trackbackquery .= '&';
+             }
+             
+             $query_token = str_replace($rewritecode, $queryreplace, $tokens[0][$i]) . preg_index($i+1, $matches);
+             $query .= $query_token;
+             $feedquery .= $query_token;
+             $trackbackquery .= $query_token;
+             }
+    ++$i;
+
+    // Add post paged stuff
+    $match .= '([0-9]+)?/?';
+    $query .= '&page=' . preg_index($i, $matches);
+
+    // Add post feed stuff
+    $feedregex = '(feed|rdf|rss|rss2|atom)/?';
+    $feedmatch .= $feedregex;
+    $feedquery .= '&feed=' . preg_index($i, $matches);
+
+    // Add post trackback stuff
+    $trackbackregex = 'trackback/?';
+    $trackbackmatch .= $trackbackregex;
+
+    // Site feed
+    $sitefeedmatch = 'feed/?([0-9a-z-]+)?/?$';
+    $sitefeedquery = $site_root . 'wp-feed.php?feed=' . preg_index(1, $matches);
+
+    // Site comment feed
+    $sitecommentfeedmatch = 'comments/feed/?([0-9a-z-]+)?/?$';
+    $sitecommentfeedquery = $site_root . 'wp-feed.php?feed=' . preg_index(1, $matches) . '&withcomments=1';
+
+    // Code for nice categories and authors, currently not very flexible
+    $front = substr($permalink_structure, 0, strpos($permalink_structure, '%'));
+    $catmatch = $front . 'category/';
+    $catmatch = preg_replace('|^/+|', '', $catmatch);
+    
+    $catfeedmatch = $catmatch . '(.*)/' . $feedregex;
+    $catfeedquery = 'wp-feed.php?category_name=' . preg_index(1, $matches) . '&feed=' . preg_index(2, $matches);
+
+    $catmatch = $catmatch . '?(.*)';
+    $catquery = 'index.php?category_name=' . preg_index(1, $matches);
+
+    $authormatch = $front . 'author/';
+    $authormatch = preg_replace('|^/+|', '', $authormatch);
+
+    $authorfeedmatch = $authormatch . '(.*)/' . $feedregex;
+    $authorfeedquery = 'wp-feed.php?author_name=' . preg_index(1, $matches) . '&feed=' . preg_index(2, $matches);
+
+    $authormatch = $authormatch . '?(.*)';
+    $authorquery = 'index.php?author_name=' . preg_index(1, $matches);
+
+    $rewrite = array(
+                     $catfeedmatch => $catfeedquery,
+                     $catmatch => $catquery,
+                     $authorfeedmatch => $authorfeedquery,
+                     $authormatch => $authorquery,
+                     $match => $query,
+                     $feedmatch => $feedquery,
+                     $trackbackmatch => $tracbackquery,
+                     $sitefeedmatch => $sitefeedquery,
+                     $sitecommentfeedmatch => $sitecommentfeedquery
+                     );
+
+    return $rewrite;
+}
+
+?>