[ci skip] ext/dom: NEWS/UPGRADING notes for asymmetric visibility on readonly properties. (#21809)

Author: devnexen

NEWS

@@ -26,6 +26,11 @@ PHP                                                                        NEWS
 - DOM:
   . Removed LIBXML_XINCLUDE from valid options for XMLDocument,
     as it was a no-op. (ndossche)
+  . Readonly DOM properties are now declared with asymmetric visibility
+    (public private(set)). ReflectionProperty::isWritable() reports them
+    correctly, and external writes raise "Cannot modify private(set)
+    property" instead of the previous readonly modification error.
+    (David Carlier)
 
 - Fileinfo:
   . Fixed bug GH-20679 (finfo_file() doesn't work on remote resources).

UPGRADING

@@ -19,6 +19,16 @@ PHP 8.6 UPGRADE NOTES
 1. Backward Incompatible Changes
 ========================================
 
+- DOM:
+  . Properties previously documented as @readonly (e.g. DOMNode::$nodeType,
+    DOMDocument::$xmlEncoding, DOMEntity::$actualEncoding, ::$encoding,
+    ::$version) are now declared with asymmetric visibility
+    (public private(set)). Attempts to write to them from outside the
+    class now raise "Cannot modify private(set) property <class>::$<prop>
+    from global scope" instead of the prior readonly modification error.
+    ReflectionProperty::isWritable() also reports these properties
+    accurately.
+
 - GD:
   . imagesetstyle(), imagefilter() and imagecrop() filter their
     array arguments types/values and raise a TypeError/ValueError