Added support for $_SERVER['CI_ENV'] in index.php
Remember this is entirely optional, nothing will change if you do not which to use Multiple Environments just like right now. If you DO set CI_ENV you can manipulate the switch that controls error reporting, etc, so set it to "production" on your live site to hide errors from users. If you don't require this logic you can remove it, or change it entirely to check HTTP_HOST for environment subdomains, or check IP address, etc.
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index a234d69..5e09f8c 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -19,6 +19,7 @@
 -  General Changes
 
    -  PHP 5.1.6 is no longer supported. CodeIgniter now requires PHP 5.2.4.
+   -  ``$_SERVER['CI_ENV']`` can now be set to control the ``ENVIRONMENT`` constant.
    -  Added an optional backtrace to php-error template.
    -  Added Android to the list of user agents.
    -  Added Windows 7, Android, Blackberry and iOS to the list of user platforms.