Fatal error: Uncaught Error: Class "PhpOffice\PhpSpreadsheet\Worksheet\CellIterator" not found in D:\xampp\htdocs\phpOffice\PhpSpreadsheet\Worksheet\ColumnCellIterator.php:12 Stack trace: #0 {main} thrown in D:\xampp\htdocs\phpOffice\PhpSpreadsheet\Worksheet\ColumnCellIterator.php on line 12