$sql = 'select generalStyle from Styles order by sequence';
$stmt = $modx->prepare($sql);
$stmt->execute();
$result = $stmt->setFetchMode(PDO::FETCH_NUM);
if (! $result) {
    $msg = $stmt->errorInfo();
    echo 'Error in "ms-mtk-getGeneralStyles" ' . $msg[2];
}
$output = '';
while ($row = $stmt->fetch()) {
    $output .= '    <option value="' . $row[0] . '">' . $row[0] . '</option>' . PHP_EOL;
}
return $output;