Add UPGRADING note for substr() behavior

[ci skip]

diff --git a/UPGRADING b/UPGRADING
index 05c8eef1e9ec98f204013084b2d7b7da6cb59d50..0c15b1ecbe9900c0661d7096e96beeaa301b6406 100644 (file)
--- a/UPGRADING
+++ b/UPGRADING
@@ -608,6 +608,9 @@ PHP 8.0 UPGRADE NOTES
   . Calling crypt() without an explicit salt is no longer supported. If you
     would like to produce a strong hash with an auto-generated salt, use
     password_hash() instead.
+  . substr(), mb_substr(), iconv_substr() and grapheme_substr() now consistently
+    clamp out-of-bounds offsets to the string boundary. Previously, false was
+    returned instead of the empty string in some cases.
 
 - Sysvmsg:
   . msg_get_queue() will now return an SysvMessageQueue object rather than a