new CONFIG_VERSION configuration option

backend.php

@@ -4120,11 +4120,20 @@
 
 	function check_configuration_variables() {
 		if (!defined('SESSION_EXPIRE_TIME')) {
-			return "SESSION_EXPIRE_TIME is undefined";
+			return "config: SESSION_EXPIRE_TIME is undefined";
 		}
 
 		if (SESSION_EXPIRE_TIME < 60) {
-			return "SESSION_EXPIRE_TIME is too low (less than 60)";
+			return "config: SESSION_EXPIRE_TIME is too low (less than 60)";
+		}
+
+		if (SESSION_EXPIRE_TIME < SESSION_COOKIE_LIFETIME_REMEMBER) {
+			return "config: SESSION_EXPIRE_TIME should be greater or equal to" .
+				"SESSION_COOKIE_LIFETIME_REMEMBER";
+		}
+
+		if (defined('DISABLE_SESSIONS') && DISABLE_SESSIONS) {
+			return "config: you have enabled DISABLE_SESSIONS. Please disable this option.";
 		}
 
 		return false;

config.php-dist

@@ -119,5 +119,9 @@
 	// Hard expiration limit for sessions. Should be
 	// >= SESSION_COOKIE_LIFETIME_REMEMBER
 
+	define('CONFIG_VERSION', 1);
+	// Expected config version. Please updated this option in config.php
+	// if necessary (after migrating all new options from this file).
+
 	// vim:ft=php
 ?>

sanity_check.php

@@ -1,10 +1,19 @@
 <?
+	define('EXPECTED_CONFIG_VERSION', 1);
+
 	if (!file_exists("config.php")) {
 		print "<b>Fatal Error</b>: You forgot to copy 
 		<b>config.php-dist</b> to <b>config.php</b> and edit it.";
 		exit;
 	}
 
+	if (CONFIG_VERSION != EXPECTED_CONFIG_VERSION) {
+			print "<b>Fatal Error</b>: Your configuration file has
+			wrong version. Please copy new options from <b>config.php-dist</b> and
+			update CONFIG_VERSION directive.";
+		exit;	
+	}
+
 	if (!file_exists("magpierss/rss_fetch.inc")) {
 		print "<b>Fatal Error</b>: You forgot to place 
 		<a href=\"http://magpierss.sourceforge.net\">MagpieRSS</a>
@@ -13,6 +22,10 @@
 		exit;
 	}
 
+		if (CONFIG_VERSION != EXPECTED_CONFIG_VERSION) {
+			return "config: your config file version is incorrect. See config.php-dist.";
+		}
+
 	if (file_exists("xml-export.php") || file_exists("xml-import.php")) {
 		print "<b>Fatal Error</b>: XML Import/Export tools (<b>xml-export.php</b>
 		and <b>xml-import.php</b>) could be used maliciously. Please remove them