title: PHPExcel return a corrupted file
body: <p>If I save it to file:</p>
  
  <pre><code>$objWriter-&gt;save("test.xls");
  </code></pre>
  
  <p>And then download from server, I can open file without any problems.</p>
  
  <p>But when I try to save into <code>php://output</code>, got corrupted file like described in <a href="https://stackoverflow.com/questions/29131751/phpexcel-return-a-corrupted-binary-file">this</a> question.</p>
  
  <p>I tried this:</p>
  
  <pre><code>ob_end_clean();
  header( "Content-type: application/vnd.ms-excel" );
  header('Content-Disposition: attachment; filename="test.xls"');
  header("Pragma: no-cache");
  header("Expires: 0");
  
  $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
  
  $objWriter-&gt;save('php://output');
  exit;
  </code></pre>
  
  <p><code>ob_end_clean();</code> doesn't help.</p>
  
  <p>I tried <code>PHPExcel_Writer_Excel2007</code> and <code>PHPExcel_Writer_Excel5</code>. Same problem.</p>
  
  <p><strong>UPD:</strong> as I can see, excell file has BOM at start ("EF BB BF"). But I've checked all my script, they don't have BOM symbol. So, does it means that PXPExcell add BOM?</p>