Sample code for php to read and download csv files

$fileName = "prefs.csv";
header('Content-Type: application/octet-stream');
header('Content-Disposition: attachment; filename=' . $ fileName);
header('Content-Transfer-Encoding: binary');
header('Content-Length: ' . filesize($fileName));
readfile($fileName);

Example 2. Download the csv file in string form.

$fileName = "pref_" . date("YmdHis") . ".csv";
header('Content-Type: application/octet-stream');
header(' Content-Disposition: attachment; filename=' . $fileName);
echo $csv;