Merge branch 2.1-stable into develop
diff --git a/user_guide_src/source/libraries/input.rst b/user_guide_src/source/libraries/input.rst
index 432bac3..7f995f0 100644
--- a/user_guide_src/source/libraries/input.rst
+++ b/user_guide_src/source/libraries/input.rst
@@ -242,6 +242,9 @@
 	     echo 'Valid';
 	}
 
+Accepts an optional second string parameter of 'ipv4' or 'ipv6' to specify
+an IP format. The default checks for both formats.
+
 $this->input->user_agent()
 ===========================