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<?php
function download_headers($filename) {
  $agentstr = getenv('HTTP_USER_AGENT');
  if (eregi('opera', $agentstr)) {
    $agent = 'OPERA';
  } elseif (eregi('msie', $agentstr)) {
    $agent = 'IE';
  } else {
    $agent = 'STD';
  }
  $mime_type = ($agent == 'IE' || $agent == 'OPERA')
    ? 'application/octetstream'
    : 'application/octet-stream';

  header('Content-Type: ' . $mime_type);
  if ($agent == 'IE') {
    header('Content-Disposition: inline; filename="'.$filename.'"');
    header('Expires: 0');
    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
    header('Pragma: public');
  } else {
    header('Content-Disposition: attachment; filename="'.$filename.'"');
    header('Expires: 0');
    header('Pragma: no-cache');
  }
}
?>