Index: includes/bootstrap.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/bootstrap.inc,v
retrieving revision 1.68
diff -u -p -r1.68 bootstrap.inc
--- includes/bootstrap.inc	19 Sep 2005 19:13:35 -0000	1.68
+++ includes/bootstrap.inc	9 Oct 2005 21:27:47 -0000
@@ -380,6 +380,16 @@ function cache_clear_all($cid = NULL, $w
 
 /**
  * Store the current page in the cache.
+ *
+ * We try to store a gzipped version of pages in the cache. This
+ * requires the PHP zlib module (http://php.net/manual/en/ref.zlib.php).
+ * Presence of this module is checked by testing for the function
+ * gzencode. There are two compression algorithms: gzip and deflate.
+ * The majority of all modern browsers supports gzip or both of them.
+ * We only save gzipped data in the cache, or uncompressed data if 
+ * zlib is not available. 
+ *
+ * @see drupal_page_header
  */
 function page_set_cache() {
   global $user, $base_url;
@@ -388,15 +398,15 @@ function page_set_cache() {
     // This will fail in some cases, see page_get_cache() for the explanation.
     if ($data = ob_get_contents()) {
       if (function_exists('gzencode')) {
-        if (version_compare(phpversion(), '4.2', '>=')) {
+        if (zlib_get_coding_type() == 'gzip') {
           $data = gzencode($data, 9, FORCE_GZIP);
         }
-        else {
-          $data = gzencode($data, FORCE_GZIP);
-        }
       }
       ob_end_flush();
-      cache_set($base_url . request_uri(), $data, CACHE_TEMPORARY, drupal_get_headers());
+      if ($data) {
+       // May be false if gzencode returned an error
+        cache_set($base_url . request_uri(), $data, CACHE_TEMPORARY, drupal_get_headers());
+      }
     }
   }
 }
@@ -569,6 +579,8 @@ function drupal_set_title($title = NULL)
 
 /**
  * Set HTTP headers in preparation for a page response.
+ *
+ * @see page_set_cache
  */
 function drupal_page_header() {
   if (variable_get('cache', 0)) {