$ie->getTextBox('name:', 'ctl00$ContentPlaceHolderContent$FileUpload_opfFile')->SetValue('C:\test\9780547076034NIMAS.opf');

$ie->getTextBox('name:', 'ctl00$ContentPlaceHolderContent$FileUpload_opfFile')->SetValue('C:/test/9780547076034NIMAS.opf');

$ie->getTextBox('name:', 'ctl00$ContentPlaceHolderContent$FileUpload_opfFile')->SetValue('C:\\test\\9780547076034NIMAS.opf');

$ie->getTextBox('name:', 'ctl00$ContentPlaceHolderContent$FileUpload_opfFile')->SetValue('C://test//9780547076034NIMAS.opf');

$ie->getTextBox('name:', 'ctl00$ContentPlaceHolderContent$FileUpload_opfFile')->SetValue("C:\test\9780547076034NIMAS.opf");

$ie->getTextBox('name:', 'ctl00$ContentPlaceHolderContent$FileUpload_opfFile')->SetValue("C:/test/9780547076034NIMAS.opf");

$ie->getTextBox('name:', 'ctl00$ContentPlaceHolderContent$FileUpload_opfFile')->SetValue("C:\\test\\9780547076034NIMAS.opf");

$ie->getTextBox('name:', 'ctl00$ContentPlaceHolderContent$FileUpload_opfFile')->SetValue("C://test//9780547076034NIMAS.opf");