diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 0000000..51fea41
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,22 @@
+# This file tells which files and directories should be ignored and
+# NOT downloaded when using composer to pull down a project with
+# the --prefer-dist option selected. Used to remove development
+# specific files so user has a clean download.
+
+# git files
+.gitattributes export-ignore
+# .gitignore
+
+# helper config files
+.travis.yml export-ignore
+phpdoc.dist.xml export-ignore
+
+# Misc other files
+readme.rst
+
+# They don't want all of our tests...
+tests/codeigniter/ export-ignore
+tests/travis/ export-ignore
+
+# User Guide Source Files
+user_guide_src
diff --git a/system/libraries/Image_lib.php b/system/libraries/Image_lib.php
index e056654..ce6c42b 100644
--- a/system/libraries/Image_lib.php
+++ b/system/libraries/Image_lib.php
@@ -1055,8 +1055,11 @@
 
 		if ($this->rotation_angle === 'hor')
 		{
-			for ($i = 0; $i < $height; $i++, $left = 0, $right = $width-1)
+			for ($i = 0; $i < $height; $i++)
 			{
+				$left = 0;
+				$right = $width - 1;
+
 				while ($left < $right)
 				{
 					$cl = imagecolorat($src_img, $left, $i);
@@ -1072,18 +1075,21 @@
 		}
 		else
 		{
-			for ($i = 0; $i < $width; $i++, $top = 0, $bot = $height-1)
+			for ($i = 0; $i < $width; $i++)
 			{
-				while ($top < $bot)
+				$top = 0;
+				$bottom = $height - 1;
+
+				while ($top < $bottom)
 				{
 					$ct = imagecolorat($src_img, $i, $top);
-					$cb = imagecolorat($src_img, $i, $bot);
+					$cb = imagecolorat($src_img, $i, $bottom);
 
 					imagesetpixel($src_img, $i, $top, $cb);
-					imagesetpixel($src_img, $i, $bot, $ct);
+					imagesetpixel($src_img, $i, $bottom, $ct);
 
 					$top++;
-					$bot--;
+					$bottom--;
 				}
 			}
 		}
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 2d10f8f..185a17a 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -27,6 +27,7 @@
 -  Fixed a bug (#3801) - :doc:`Output Library <libraries/output>` method ``_display_cache()`` incorrectly looked for the last modified time of a directory instead of the cache file.
 -  Fixed a bug (#3816) - :doc:`Form Validation Library <libraries/form_validation>` treated empty string values as non-existing ones.
 -  Fixed a bug (#3823) - :doc:`Session Library <libraries/sessions>` drivers Redis and Memcached didn't properly handle locks that are blocking the request for more than 30 seconds.
+-  Fixed a bug (#3846) - :doc:`Image Manipulation Library <libraries/image_lib>` method `image_mirror_gd()` didn't properly initialize its variables.
 
 Version 3.0.0
 =============
diff --git a/user_guide_src/source/libraries/form_validation.rst b/user_guide_src/source/libraries/form_validation.rst
index da43a4b..dbf1e8a 100644
--- a/user_guide_src/source/libraries/form_validation.rst
+++ b/user_guide_src/source/libraries/form_validation.rst
@@ -946,6 +946,7 @@
 ========================= ========== ============================================================================================= =======================
 **required**              No         Returns FALSE if the form element is empty.
 **matches**               Yes        Returns FALSE if the form element does not match the one in the parameter.                    matches[form_item]
+**regex_match**           Yes        Returns FALSE if the form element does not match the regular expression.                      regex_match[/regex/]
 **differs**               Yes        Returns FALSE if the form element does not differ from the one in the parameter.              differs[form_item]
 **is_unique**             Yes        Returns FALSE if the form element is not unique to the table and field name in the            is_unique[table.field]
                                      parameter. Note: This rule requires :doc:`Query Builder <../database/query_builder>` to be