public function toHTML($width=2)
    {
        print('<table style="background-color:#eee;">');
        for ($i = 0; $i < $this->m; $i++) {
            print('<tr>');
            for ($j = 0; $j < $this->n; $j++) {
                print('<td style="background-color:#fff;border:1px solid #000;padding:2px;text-align:center;vertical-align:middle;">' . $this->A[$i][$j] . '</td>');
            }
            print('</tr>');
        }
        print('</table>');
    }