diff --git a/src/utils/utf8.php b/src/utils/utf8.php
--- a/src/utils/utf8.php
+++ b/src/utils/utf8.php
@@ -289,7 +289,14 @@
  */
 function phutil_utf8_strlen($string) {
   if (function_exists('utf8_decode')) {
-    return strlen(utf8_decode($string));
+    // historically, this was just a call to strlen(utf8_decode())
+    // but, since PHP 8.2 that function is deprecated, so this is
+    // the current equivalent.
+    // TODO: probably we can just adopt mb_strlen($string, 'ISO-8859-1')
+    // but I'm not bold enough to change this so deeply in this phase,
+    // where my goal was just to fix PHP 8.2.
+    // https://we.phorge.it/T15188
+    return strlen(mb_convert_encoding($string, 'ISO-8859-1'));
   }
   return count(phutil_utf8v($string));
 }