$objPHPExcel1 = PHPExcel_IOFactory::load("MergeBook1.xlsx");
$objPHPExcel2 = PHPExcel_IOFactory::load("MergeBook2.xlsx");
foreach($objPHPExcel2->getSheetNames() as $sheetName) {
$sheet = $objPHPExcel2->getSheetByName($sheetName);
$sheet->setTitle($sheet->getTitle() . ' copied');
$objPHPExcel1->addExternalSheet($sheet);
}
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel1, 'Excel2007');
$objWriter->save('mergedBooks.xlsx');