header("Content-Type: application/zip") and header("Content-Disposition: attachment; filename=$fileName") not working in wordpress?

The above two function not working in wordpress. I want to download file and i am running wordpress in xampp also i have tried it in another online server with wordpress framework still not working.

but this is working in another online server where i have not used wordpress framework.

Is there is problem with wordpress using the above two function?

 header("Content-Type: application/zip")
 header("Content-Disposition: attachment; filename=$fileName");

via Chebli Mohamed