title: How to open an Excel file with PHPExcel for both reading and writing?
body: <p>I'm using the PHPExcel library, and I'm creating xls objects either for writing or for reading:  </p>
  
  <p><code>PHPExcel_IOFactory::createReaderForFile('file.xlsx')</code><br>
  <code>PHPExcel_IOFactory::createWriter('Excel2007')</code>  </p>
  
  <p>How can I open an XLSX file for reading and writing?  </p>