Since you already have the data, just output the headers and then the data!
<?php
header('Pragma: public');
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
header('Cache-Control: private',false);
header("Content-type: application/force-download"); // or application/octet-stream
header('Content-Disposition: attachment; filename="ups.gif"');
header('Content-Transfer-Encoding: binary');
header('Connection: close');
echo $label_data;
exit;
?>