Try out with the below example code:
$file = 'ASDFGgg.pdf';
_Download("mypath/file.zip/".$file, $file);
function _Download($f_location,$f_name){
header ("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header('Content-Description: File Transfer');
header('Content-Type: application/octet-stream');
header('Content-Length: ' . filesize($f_location));
header('Content-Disposition: attachment; filename=' . basename($f_name));
readfile($f_location);
}
Hope this helps.