write csv with fputcsv() directly to php://output

exportcsv.php

$filename="export.csv";
header("Content-type: application/octet-stream");
header("Content-Disposition: attachment; filename=$filename");
header("Pragma: no-cache");
header("Expires: 0");
$csv = fopen('php://output', 'w');

foreach($rows as $ind=>$row){
	if($ind==0)
		fputcsv($csv,array_keys($row));
	fputcsv($csv,$row);
}
fclose($csv);

exit();