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//load current worksheet
$file1 = "path to file";
$PhpSpreadsheet = $reader->load($file1);
//load worksheet from template
$template = "path to file";
$PhpSpreadsheet1 = $reader->load($template);
//clone into current worksheet
$cloneWorksheet = clone $PhpSpreadsheet1->getActiveSheet()->copy();
$PhpSpreadsheet->addExternalSheet($cloneWorksheet);
$PhpSpreadsheet->setActiveSheetIndex($PhpSpreadsheet->getIndex($cloneWorksheet));
$PhpSpreadsheet->getActiveSheet()->setTitle("Title 1"));
unset($PhpSpreadsheet);
unset($PhpSpreadsheet1);
note that you have to add addExternalSheet() before setTitle() otherwise you will get error: Sheet does not exist