Remove deprecated ReflectionFunction->isDisabled() call

demos/Demo/Highlighter.php

@@ -12,22 +12,17 @@
 
 namespace Demo;
 
-use ReflectionFunction;
-
 /**
  * Highlighter utility class
  */
 final class Highlighter
 {
     /**
      * Highlighter with built-in check for list of disabled function (Google AppEngine)
-     *
-     * @param string $file Name of the file
      */
     public static function highlight(string $file): void
     {
-        $highlightFileFunc = new ReflectionFunction('highlight_file');
-        if (!$highlightFileFunc->isDisabled()) {
+        if (function_exists('highlight_file')) {
             highlight_file($file);
         } else {
             echo '<pre>' . htmlspecialchars(file_get_contents($file)) . '</pre>';