Convert PHP array to csv (without saving to file)

<?php

    $data = array();
    $stream = fopen("php://temp", 'w');
    foreach($data as $key => $val) {
        fputcsv($stream, $val);
    }
    rewind($stream);
    $data = stream_get_contents($stream);
    fclose($stream);

    header('Content-Description: File Transfer');
    header('Content-Type: text/csv');
    header('Content-Disposition: attachment; filename=data.csv');
    header('Expires: 0');
    header('Cache-Control: must-revalidate');
    header('Pragma: public');

    echo $data;

?>