Yo sacaria este código:
Código PHP:
<?php
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Content-Length: " . strlen($out));
// Output to browser with appropriate mime type, you choose ;)
header("Content-type: text/x-csv");
//header("Content-type: text/csv");
//header("Content-type: application/csv");
header("Content-Disposition: attachment; filename=$filename");
echo $out;
exit;
?>
y lo colocaría en el primer script.