public function getHtmlPreview($numLines = 5)
    {
        $html = '<table>';
        if ($this->header) {
            $html .= '<thead><tr>';
            foreach ($this->header as $h) {
                $html .= '<th>' . htmlentities($h, ENT_QUOTES, 'UTF-8') . '</th>';
            }
            $html .= '</tr></thead>';
        }
        $html .= '<tbody>';
        $i = 0;
        foreach ($this as $line) {
            if ($i >= $numLines) {
                break;
            }
            $html .= '<tr>';
            foreach ($line as $v) {
                $html .= '<td>' . htmlentities($v, ENT_QUOTES, 'UTF-8') . '</td>';
            }
            $html .= '</tr>';
            $i++;
        }
        $html .= '</tbody></table>';

        return $html;
    }