Fatal error: Uncaught Exception: Composer autoloader could not be found. Install dependencies with `composer install` and try again. in C:\xampp\htdocs\pruebas\PhpSpreadsheet\src\Bootstrap.php:22 Stack trace: #0 C:\xampp\htdocs\pruebas\PhpSpreadsheet\samples\Header.php(9): require_once() #1 C:\xampp\htdocs\pruebas\PhpSpreadsheet\samples\index.php(3): require_once('C:\\xampp\\htdocs...') #2 {main} thrown in C:\xampp\htdocs\pruebas\PhpSpreadsheet\src\Bootstrap.php on line 22