Fatal error: Uncaught Error: Class "PhpOffice\PhpSpreadsheet\Helper\Sample" not found in D:\xampp\htdocs\express\vendor\phpoffice\phpspreadsheet\samples\Header.php:11 Stack trace: #0 D:\xampp\htdocs\express\vendor\phpoffice\phpspreadsheet\samples\index.php(3): require_once() #1 {main} thrown in D:\xampp\htdocs\express\vendor\phpoffice\phpspreadsheet\samples\Header.php on line 11