Stream a downloadable CSV report in PHP

<?php

declare(strict_types=1);

/** Stream rows as a CSV download without holding the file in memory. */
function send_csv(array $rows, string $filename = 'export.csv'): void
{
    header('Content-Type: text/csv; charset=utf-8');
    header('Content-Disposition: attachment; filename="' . basename($filename) . '"');

    $stream = fopen('php://output', 'wb');
    if ($stream === false) {
        throw new RuntimeException('cannot open output stream');
    }

    // UTF-8 BOM so spreadsheet apps detect the encoding.
    fwrite($stream, "\xEF\xBB\xBF");
    foreach ($rows as $row) {
        fputcsv($stream, array_values($row));
    }
    fclose($stream);
}

$authors = [
    ['name' => 'Ada Lovelace', 'snippets' => 12],
    ['name' => 'Grace Hopper', 'snippets' => 9],
];

send_csv($authors, 'authors.csv');