Fatal error: Uncaught Error: Undefined constant "PHPEXCEL_ROOT" in D:\xampp\htdocs\PHPExcel\Autoloader.php:70 Stack trace: #0 D:\xampp\htdocs\PHPExcel\Autoloader.php(11): PHPExcel_Autoloader::load('...') #1 {main} thrown in D:\xampp\htdocs\PHPExcel\Autoloader.php on line 70