Fatal error: Uncaught Error: Undefined constant "PHPEXCEL_ROOT" in C:\xampp\htdocs\electronica\vendor\phpoffice\phpexcel\Classes\PHPExcel\Autoloader.php:77 Stack trace: #0 C:\xampp\htdocs\electronica\vendor\phpoffice\phpexcel\Classes\PHPExcel\Autoloader.php(36): PHPExcel_Autoloader::Load('PHPExcel_Shared...') #1 {main} thrown in C:\xampp\htdocs\electronica\vendor\phpoffice\phpexcel\Classes\PHPExcel\Autoloader.php on line 77