new option: ENABLE_GZIP_OUTPUT

backend.php

@@ -63,7 +63,12 @@
 	if ((!$op || $op == "rpc" || $op == "rss" || $op == "view" || 
 			$op == "digestSend" || $op == "viewfeed" || $op == "publish" ||
 			$op == "globalUpdateFeeds") && !$_REQUEST["noxml"]) {
-		header("Content-Type: application/xml; charset=utf-8");
+				header("Content-Type: application/xml; charset=utf-8");
+
+				if (ENABLE_GZIP_OUTPUT) {
+					ob_start("ob_gzhandler");
+				}
+				
 		} else {
 		if (!$_REQUEST["noxml"]) {
 			header("Content-Type: text/html; charset=utf-8");

config.php-dist

@@ -180,7 +180,11 @@
 	// Allow users to select the library to update feeds with - e.g.
 	// Magpie or SimplePie
 
-	define('CONFIG_VERSION', 15);
+	define('ENABLE_GZIP_OUTPUT', false);
+	// Selectively gzip output to improve wire performance. This requires
+	// PHP Zlib extension on the server.
+
+	define('CONFIG_VERSION', 16);
 	// Expected config version. Please update this option in config.php
 	// if necessary (after migrating all new options from this file).
 

sanity_check.php

@@ -1,7 +1,7 @@
 <?php
 	require_once "functions.php";
 
-	define('EXPECTED_CONFIG_VERSION', 15);
+	define('EXPECTED_CONFIG_VERSION', 16);
 	define('SCHEMA_VERSION', 37);
 
 	if (!file_exists("config.php")) {