foreach (categoryArrayShow('last', 'index') as $key_row)
{
    $content .= '<tr>';
    foreach ($key_row as $key_col)
    {
        $content .= "<td>$key_col[file_name]</td>";
    }
    $content .= '</tr>';
}

<table width="100%" border="0" cellpadding="0" cellspacing="0">
    {foreach from= item=}
    <tr>
        {foreach from= item=}
        <td><td>
        {/foreach}
    </tr>
    {/foreach}
</table>