Formit: send form data as attachment

$tmpFilename = $modx->cacheManager->getCachePath() . uniqid('formitcsv', true) . '.cache.php';
$fields = $hook->getValues();

// create CSV
$fp = fopen($tmpFilename, 'w');
fputcsv($fp, array_keys($fields));
fputcsv($fp, $fields);
fclose($fp);

// attach File to FormIt
$hook->setValue('attachment', array(
    'tmp_name' => $tmpFilename,
    'name'     => 'FormIt.csv',
    'size' => filesize($tmpFilename)
));