set_header() file download problem

CI 3.0.3. Here is my question on stackoverflow: http://stackoverflow.com/questions/34432...-size-n-kb

Further investigation revealed the fact that CI's set_header() method doesn't send 'Content-Disposition' header:



In other words, $this->output->set_header() does not work, while php's native header() with the same param - works.

CAUSES PROBLEM:

PHP Code:

$this->output->set_header('Content-Description: File Transfer');
$this->output->set_header('Content-Type: application/octet-stream');
$this->output->set_header('Content-Disposition: attachment; filename="Segmentation ' . $date->format('Y-m-d H:i:s') . '.' . $format . '"');
$this->output->set_header('Expires: 0');
$this->output->set_header('Cache-Control: must-revalidate');
$this->output->set_header('Pragma: public');
$this->output->set_header('Content-Length: ' . strlen($str));
echo $str;
exit(); 


CORRECT:

PHP Code:

header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename="Segmentation ' . $date->format('Y-m-d H:i:s') . '.' . $format . '"');
header('Expires: 0');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header('Content-Length: ' . strlen($str));
echo $str;
exit(); 


Is it bug?