Fatal error: Uncaught Error: Interface 'PHPExcel_Writer_IWriter' not found in /var/www/testing/PHPExcel_1.7.8/Classes/PHPExcel/Writer/HTML.php:36 Stack trace: #0 {main} thrown in /var/www/testing/PHPExcel_1.7.8/Classes/PHPExcel/Writer/HTML.php on line 36