diff --git a/functions/filesystem.xml b/functions/filesystem.xml
index 0662499849..d27827affe 100644
--- a/functions/filesystem.xml
+++ b/functions/filesystem.xml
@@ -330,6 +330,36 @@ $df = diskfreespace("/"); // $df contains the number of bytes
    </refsect1>
   </refentry>
 
+  <refentry id="function.disk-total-space">
+   <refnamediv>
+    <refname>disk_total_space</refname>
+    <refpurpose>Returns the total size of a directory</refpurpose>
+   </refnamediv>
+   <refsect1>
+    <title>Description</title>
+    <funcsynopsis>
+     <funcprototype>
+      <funcdef>float <function>disk_total_space</function></funcdef>
+      <paramdef>string <parameter>directory</parameter></paramdef>
+     </funcprototype>
+    </funcsynopsis>
+    <para>
+     Given a string containing a directory, this function will return
+     the total number of bytes on the corresponding filesystem or disk
+     partition.
+    </para>
+    <para>
+     <example>
+      <title><function>disk_total_space</function> example</title>
+      <programlisting role="php">
+$df = disk_total_space("/"); // $df contains the total number of
+                             // bytes available on "/"
+      </programlisting>
+     </example>
+    </para>
+   </refsect1>
+  </refentry>
+
   <refentry id="function.fclose">
    <refnamediv>
     <refname>fclose</refname>