“Excel found unreadable content” warning when opening Excel files made with PHPExcel

Question

I\'m trying to download Excel files (xlsx) using PHPExcel as follows.

require_once(\"../../phpExcel/Classes/PHPExcel.php\");
require_once(\"../../phpExcel/Cl         


        

Answer 1

Give the active sheet a title:

$sheet->setTitle('Some title string here');