title: PHPExcel generating corrupted file - ob_end_clean() not working
body: <p>I'm trying to generate a <strong>.xlsx</strong> file using <strong>PHPExcel</strong>. The process is generating the file, but when I'm getting to open the file, It says It's corrupted. When I use <em>Open and Repair</em>, the file opens and It's ok, but I don't want to repair everytime I generate the file. I tried to use the function <code>ob_end_clean()</code> before saving, but It didn't work.</p>
  
  <p>Here is the code I'm using:</p>
  
  <pre><code>$objSheet1 = $objPHPExcel-&gt;getActiveSheet();
  $objSheet1-&gt;setTitle("sheet1");
  $line_value = 1;
  foreach($sheet1_data as $line){
      $col = 'A';
      foreach($line as $cell_value){
          $objSheet1-&gt;setCellValue($col.$line_value, $cell_value);
          $col++;
      }
      $line_value++;
  }
  
  $objSheet2 = $objPHPExcel-&gt;createSheet();
  $objSheet2-&gt;setTitle("sheet2");
  $line_value = 1;
  foreach($sheet2_data as $line){
      $col = 'A';
      foreach($line as $cell_value){
          $objSheet2-&gt;setCellValue($col.$line_value, $cell_value);
          $col++;
      }
      $line_value++;
  }
  
  ob_end_clean();
  $objWriter = PHPExcel_IOFactory::createWriter ( $objPHPExcel, 'Excel2007' );
  $objWriter-&gt;save ( get_file_location() );
  </code></pre>