As far as I know, php-excel-reader does not support xlsx. PHPExcel is the way to go. It is believed that it is better to store everything that is in your xslx files, less proprietary. Having taken a long shot, I would suggest that your xslx does not contain the calculations that belong to the xlsx files, but rather the table data that is better stored in some database (txt, csv, sqlite, database server).
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