diff --git a/reference/funchand/functions/register-shutdown-function.xml b/reference/funchand/functions/register-shutdown-function.xml
index eadd4f318f..ca011f1e38 100644
--- a/reference/funchand/functions/register-shutdown-function.xml
+++ b/reference/funchand/functions/register-shutdown-function.xml
@@ -142,6 +142,14 @@ register_shutdown_function('shutdown');
     under some web servers, e.g. Apache.
    </para>
   </note>
+  <note>
+   <para>
+    Shutdown functions will not be executed if the process is killed with a SIGTERM
+    or SIGKILL signal. While you cannot intercept a SIGKILL, you can use <function>pcntl_signal</function>
+    to install a handler for a SIGTERM which uses <function>exit</function> to
+    end cleanly.
+   </para>
+  </note>
  </refsect1>
 
  <refsect1 role="seealso">