Fatal error: Uncaught Exception: Composer autoloader could not be found. Install dependencies with `composer install` and try again. in /var/www/html/lib/php-spreadsheet/samples/Bootstrap.php:22 Stack trace: #0 /var/www/html/lib/php-spreadsheet/samples/Header.php(9): require_once() #1 /var/www/html/lib/php-spreadsheet/samples/index.php(3): require_once('/var/www/html/l...') #2 {main} thrown in /var/www/html/lib/php-spreadsheet/samples/Bootstrap.php on line 22