Input, Session and Cookie get's will return NULL.
Read more about this change here:
http://codeigniter.com/forums/viewthread/215833
diff --git a/user_guide_src/source/libraries/uri.rst b/user_guide_src/source/libraries/uri.rst
index ee60b77..cdd76e3 100644
--- a/user_guide_src/source/libraries/uri.rst
+++ b/user_guide_src/source/libraries/uri.rst
@@ -25,7 +25,7 @@
#. metro
#. crime_is_up
-By default the function returns FALSE (boolean) if the segment does not
+By default the function returns NULL if the segment does not
exist. There is an optional second parameter that permits you to set
your own default value if the segment is missing. For example, this
would tell the function to return the number zero in the event of