I'm using a Wordpress plugin, wpdatatables, that uses PHPExcel to produce pdf, csv, and Excel file exports.
Anyway, when downloading an .xls file from my website, when I open it .. Excel gives me the error “The file format and extension of “blahblah.xls” don’t match. The file could be corrupted or unsafe. Unless you trust its source, don’t open it.”
Of course the file still opens fine, but I'd like to get rid of this error. One thing I noticed is the .CSV export is seemingly identical in all ways except the file extension, and opens without an error.
As someone who is not terribly familiar with PHP sadly, what direction should I look in to make PHPExcel produce .csv files only? Is there a specific function or directory in PHPExcel responsible for the Excel writer file output?