//definição do cabeçalho
header('Content-Type: application/vnd.ms-excel;');
header('Content-Disposition: attachment;filename=plan.xls');
header('Content-Transfer-Encoding: binary');
header('Cache-Control: max-age=0');

//cria uma planilha no formato do excel 2003
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel5');
$objWriter->save('php://output');