PHP 8.1 | MigrationGuide/New classes: add missing classes

> Added `CURLStringFile`, which can be used to post a file from a string rather than a file

Refs:
* https://github.com/php/php-src/blob/f67986a9218f4889d9352a87c29337a5b6eaa4bd/UPGRADING#L231-L235
* php/php-src#6456
* php/php-src@e727919

As part of the Fibers RFC/PR, the Reflection extension also received a new class.

* https://wiki.php.net/rfc/fibers
* php/php-src#6875
* php/php-src@c276c16

Note: I've not listed the `Fiber` and `FiberError` classes as those could be considered covered via the mention of Fibers on the "New Features" page, though happy to update the commit if so desired.

Co-authored-by: jrfnl <[email protected]>

Closes GH-1447.

Author: jrfnl

appendices/migration81/new-classes.xml

@@ -2,6 +2,18 @@
 <sect1 xml:id="migration81.new-classes" xmlns:xlink="http://www.w3.org/1999/xlink">
  <title>New Classes and Interfaces</title>
 
+ <sect2 xml:id="migration81.new-classes.curl">
+  <title>cURL</title>
+
+  <itemizedlist>
+   <listitem>
+    <simpara>
+     <classname>CURLStringFile</classname>
+    </simpara>
+   </listitem>
+  </itemizedlist>
+ </sect2>
+
  <sect2 xml:id="migration81.new-classes.intl">
   <title>Intl</title>
 
@@ -14,6 +26,18 @@
   </itemizedlist>
  </sect2>
 
+ <sect2 xml:id="migration81.new-classes.reflection">
+  <title>Reflection</title>
+
+  <itemizedlist>
+   <listitem>
+    <simpara>
+     <classname>ReflectionFiber</classname>
+    </simpara>
+   </listitem>
+  </itemizedlist>
+ </sect2>
+
 </sect1>
 <!-- Keep this comment at the end of the file
 Local variables: