Merge pull request #3850 from RodolfoSilva/develop

[ci skip] Add missing docs for 'regex_match' form validation rule
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