Fix #73267: Order by callback changed

While users are not supposed to rely on a stable sort anyway, it
may be helpful to explicitly mention possible sort order changes
in the migration guides.

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@340557 c90b9560-bf6c-de11-be94-00142212c4b1

appendices/migration70/incompatible/other.xml

@@ -359,6 +359,21 @@ switch (1) {
    had been modified. Now, they will always return the current argument values.
   </para>
  </sect3>
+
+ <sect3 xml:id="migration70.incompatible.other.sort-order">
+  <title>Sort order of equal elements</title>
+  <para>
+   The internal sorting algorithm has been improved, what may result in
+   different sort order of elements, which compare as equal, than before.
+  </para>
+  <note>
+   <para>
+    Don't rely on the order of elements which compare as equal; it might change
+    anytime.
+   </para>
+  </note>
+ </sect3>
+
 </sect2>
 
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appendices/migration71/incompatible.xml

@@ -308,6 +308,20 @@ array(2) {
   </informalexample>
  </sect2>
 
+ <sect2 xml:id="migration70.incompatible.sort-order">
+  <title>Sort order of equal elements</title>
+  <para>
+   The internal sorting algorithm has been improved, what may result in
+   different sort order of elements, which compare as equal, than before.
+  </para>
+  <note>
+   <para>
+    Don't rely on the order of elements which compare as equal; it might change
+    anytime.
+   </para>
+  </note>
+ </sect2>
+
 </sect1>
 
 <!-- Keep this comment at the end of the file