使用php下载splitted csv文件

Question

I am splitting huge csv file into small chunks which i am able to able to, but i want it to download splitted parts. how can i do it

Here is my code:

$a=$_FILES['file']['tmp_name'];
$inputFile = $a;
$outputFile = 'splitk';

$splitSize = 50000;

$in = fopen($inputFile, 'r');

$rowCount = 0;
$fileCount = 1;
while (!feof($in)) {
if (($rowCount % $splitSize) == 0) {
    if ($rowCount > 0) {
        fclose($out);
    }
    $out = fopen($outputFile . $fileCount++ . '.csv', 'w');
}
$data = fgetcsv($in);
if ($data){
fputcsv($out, $data);}

header('Content-type: text/csv');
header('Content-Disposition: attachment; filename="'.$out.'"'); 
header("Pragma: no-cache"); 
header("Expires: 0");

$rowCount++;

}


fclose($out);