diff --git a/reference/strings/functions/substr-compare.xml b/reference/strings/functions/substr-compare.xml
index 9925dc92b1..c2851be4d5 100644
--- a/reference/strings/functions/substr-compare.xml
+++ b/reference/strings/functions/substr-compare.xml
@@ -1,5 +1,5 @@
 <?xml version='1.0' encoding='iso-8859-1'?>
-<!-- $Revision: 1.6 $ -->
+<!-- $Revision: 1.7 $ -->
 <refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.substr-compare">
  <refnamediv>
   <refname>substr_compare</refname>
@@ -45,7 +45,8 @@
      <term><parameter>offset</parameter></term>
      <listitem>
       <para>
-       The start position for the comparison.
+       The start position for the comparison. If negative, it starts counting
+       from the end of the string.
       </para>
      </listitem>
     </varlistentry>
@@ -82,6 +83,30 @@
   </para>
  </refsect1>
 
+ <refsect1 role="changelog">
+  &reftitle.changelog;
+  <para>
+   <informaltable>
+    <tgroup cols="2">
+     <thead>
+      <row>
+       <entry>&Version;</entry>
+       <entry>&Description;</entry>
+      </row>
+     </thead>
+     <tbody>
+      <row>
+       <entry>5.1.0</entry>
+       <entry>
+        Added the possibility to use a negative <parameter>offset</parameter>.
+       </entry>
+      </row>
+     </tbody>
+    </tgroup>
+   </informaltable>
+  </para>
+ </refsect1>
+
  <refsect1 role="examples">
   &reftitle.examples;
   <para>
@@ -91,6 +116,7 @@
 <![CDATA[
 <?php
 echo substr_compare("abcde", "bc", 1, 2); // 0
+echo substr_compare("abcde", "de", -2, 2); // 0
 echo substr_compare("abcde", "bcg", 1, 2); // 0
 echo substr_compare("abcde", "BC", 1, 2, true); // 0
 echo substr_compare("abcde", "bc", 1, 3); // 1