Make set_status_header() a dummy under CLI

Close #3605
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 3145e83..a904c82 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -507,7 +507,8 @@
       -  Changed internal function ``load_class()`` to accept a constructor parameter instead of (previously unused) class name prefix.
       -  Removed default parameter value of :php:func:`is_php()`.
       -  Added a second argument ``$double_encode`` to :php:func:`html_escape()`.
-      -  Changed function ``config_item()`` to return NULL instead of FALSE when no value is found.
+      -  Changed function :php:func:`config_item()` to return NULL instead of FALSE when no value is found.
+      -  Changed function :php:func:`set_status_header()` to return immediately when run under CLI.
 
    -  :doc:`Output Library <libraries/output>` changes include: