// outputs json
header('Content-Disposition: attachment; filename=output.json');
header('Content-Type: application/json');
echo json_encode($output);

// output json
header('Content-Disposition: attachment; filename=output.js');
header('Content-Type: text/javascript');
$json = json_encode($output);

// it's dirty
$json = 'var myObject = ' . $json . ';';

echo $json