Fix sample code in migration85.new-features

php/doc-en@ce39734

Author: mumumu

appendices/migration85/new-features.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <!-- $Revision$ -->
-<!-- EN-Revision: ec45af749649dc0d6a23eaedeed1b601f7460813 Maintainer: mumumu Status: ready --> 
+<!-- EN-Revision: ce397343296708654c8cdac774e23a9ee47ab27d Maintainer: mumumu Status: ready -->
 <sect1 xml:id="migration85.new-features" xmlns:xlink="http://www.w3.org/1999/xlink">
  <title>新機能</title>
 
@@ -75,7 +75,7 @@ print $result . PHP_EOL;  // Prints "11"
 
 #[\NoDiscard]
 function concat(string $a, string $b): string {
-     return a + b;
+     return $a . $b;
 }
 
 // Warning: The return value of function concat() should either be used or