diff --git a/functions/strings.xml b/functions/strings.xml
index 7a532ac5c1..eb5f350cc5 100644
--- a/functions/strings.xml
+++ b/functions/strings.xml
@@ -1337,6 +1337,33 @@ echo '<A HREF="http://x.com/department_list_script/',
    </refsect1>
   </refentry>
 
+  <refentry id="function.rtrim">
+   <refnamediv>
+    <refname>rtrim</refname>
+    <refpurpose>Remove trailing whitespace.</refpurpose>
+   </refnamediv>
+   <refsect1>
+    <title>Description</title>
+    <funcsynopsis>
+     <funcdef>string <function>rtrim</function></funcdef>
+     <paramdef>string <parameter>str</parameter></paramdef>
+    </funcsynopsis>
+    <para>
+     Returns the argument string without trailing whitespace,
+     including newlines.  This is an alias for <function>chop</function>.
+     <example>
+      <title><function>rtrim</function> example</title>
+      <programlisting role="php">
+$trimmed = rtrim ($line);
+      </programlisting>
+     </example>
+    </para>
+    <para>
+     See also <function>trim</function>, <function>ltrim</function>.
+    </para>
+   </refsect1>
+  </refentry>
+
   <refentry id="function.setlocale">
    <refnamediv>
     <refname>setlocale</refname>