diff --git a/functions/filesystem.xml b/functions/filesystem.xml
index 1b34b88f68..0b73d24249 100644
--- a/functions/filesystem.xml
+++ b/functions/filesystem.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="iso-8859-1"?>
-<!-- $Revision: 1.115 $ -->
+<!-- $Revision: 1.116 $ -->
  <reference id="ref.filesystem">
   <title>Filesystem functions</title>
   <titleabbrev>Filesystem</titleabbrev>
@@ -1923,15 +1923,10 @@ if($fp){
    </refnamediv>
    <refsect1>
     <title>Description</title>
-     <methodsynopsis>
-      <type>bool</type><methodname>is_uploaded_file</methodname>
-      <methodparam><type>string</type><parameter>filename</parameter></methodparam>
-     </methodsynopsis>
-
-    <para>
-     This function is available only in versions of PHP 3 after PHP
-     3.0.16, and in versions of PHP 4 after 4.0.2.
-    </para>
+    <methodsynopsis>
+     <type>bool</type><methodname>is_uploaded_file</methodname>
+     <methodparam><type>string</type><parameter>filename</parameter></methodparam>
+    </methodsynopsis>
 
     <para>
      Returns &true; if the file named by <varname>filename</varname> was
@@ -1948,6 +1943,43 @@ if($fp){
      system.
     </para>
 
+    <para>
+     <function>is_uploaded_file</function> is available only in
+     versions of PHP 3 after PHP 3.0.16, and in versions of PHP 4
+     after 4.0.2. If you are stuck using an earlier version, you can
+     use the following function to help protect yourself:
+     <note>
+      <para>
+       This will <emphasis>not</emphasis> work in versions of PHP 4
+       after 4.0.2. It depends on internal functionality of PHP which
+       changed after that version.
+      </para>
+     </note>
+     <programlisting role="php">
+<![CDATA[
+<?php
+/* Userland test for uploaded file. */
+function is_uploaded_file($filename) {
+    if (!$tmp_file = get_cfg_var('upload_tmp_dir')) {
+        $tmp_file = dirname(tempnam('', ''));
+    }
+    $tmp_file .= '/' . basename($filename);
+    /* User might have trailing slash in php.ini... */
+    return (ereg_replace('/+', '/', $tmp_file) == $filename);
+}
+
+/* This is how to use it, since you also don't have
+ * move_uploaded_file() in these older versions: */
+if (is_uploaded_file($HTTP_POST_FILES['userfile'])) {
+    copy($HTTP_POST_FILES['userfile'], "/place/to/put/uploaded/file");
+} else {
+    echo "Possible file upload attack: filename '$HTTP_POST_FILES[userfile]'.";
+}
+?>
+]]>
+     </programlisting>
+    </para>
+
     <para>
      See also <function>move_uploaded_file</function>, and the section
      <link linkend="features.file-upload">Handling file uploads</link>