Hello,
If you don't set a fixed width value then the table grows to fit the content.
Please set widths for all cols of the first row:
$html = '<table>
<tbody>
<tr>
<td width="180">FY 1</td>
<td width="180">FY 2</td>
<td width="180">FY 3</td>
<td width="180">FY 4</td>
<td width="100">FY 5</td>
</tr>
<tr>
<td>Content A1</td>
<td>Content A2</td>
<td>Content A3</td>
<td>Content A4</td>
<td>Content A5</td>
</tr>
Regards.