title: PHPOffice/PHPExcel File cannot open file because the file format or file extension is not valid
body: <p>Just git cloned the latest branch to my MacBook Pro, not even the included Excel 2007 examples work. Upon running the 01simple-download-xlsx.php script I get the following error from Excel: <strong>"File cannot open file because the file format or file extension is not valid"</strong> However the 01simple-download-xls.php (Excel 2003) works 100%</p>
  
  <p>I have tried the following answers from stackoveflow:</p>
  
  <ol>
  <li>Edited the generated file with vim and found that it's empty with a 0 byte file size, although it does seem to have a blank line at the top.</li>
  <li>Full error logging is on by default but no errors shown in aforementioned file.</li>
  <li>Tried ob_start(), ob_clean() made no difference.</li>
  <li>Set the header to encode the file as utf8 without BOM.</li>
  <li>Ensured that the required PHP extensions are loaded on my system.</li>
  </ol>
  
  <p>I'm sure the problem lies with my local setup but cant seem to find the problem. Running OS X El Capitan with XAMPP as my stack server. PHP version is 5.6.3.</p>
  
  <p>Any help would be appreciated.</p>