How do I divide a row in sub rows?

Question

If I want to divide a row into some sub-rows in Drupal 8, what should the code be?

The following code worked fine for simple tables. I need to do something with the $rows array to divide the rows in sub-rows. How can I achieve this?

$form['mytable'] = array(
  '#theme'  => 'table',
  '#header' => $header,
  '#rows'   => $rows,
  '#empty'  => t('Not Found.'),
);

Answer 1

Drupal 8:

$table = [
  '#type' => 'table',
  '#header' => ['ab', 'cd', 'ef'],
  [
    [
      '#plain_text' => 'rowspan',
      '#wrapper_attributes' => ['rowspan' => 2],
    ],
    ['#markup' => '1'],
    ['#markup' => '1'],
  ],
  [['#markup' => '1'], ['#markup' => '1']],
];

Result:

See Drupal Documentation for a colspan example

Answer 2

This is still similar to how it was done in Drupal 7 and Drupal 6 with the use of colspan or rowspan attributes. The documentation for template_preprocess_table states

Each cell can be either a string or an associative array with the following keys:

• data: The string or render array to display in the table cell.
• header: Indicates this cell is a header.
• Any HTML attributes, such as "colspan", to apply to the table cell.

So the top row of your example image would be like such:

$rows = [
  [
    ['data' => '', 'attributes' => ['rowspan' => 3]],
    '',
    '',
    '',
  ],
  ['', '', ''],
  ['', '', ''],
];

in order to get the following HTML:

<tr>
  <td rowspan="3"></td>
  <td></td>
  <td></td>
  <tD></td>
</tr>
<tr>
  <td></td>
  <td></td>
  <td></td>
</tr>
<tr>
  <td></td>
  <td></td>
  <td></td>
</tr>