Table in custom form + empty values in form_state

Question

In a custom form I created a table element:

  // Table results.
  $form['table'] = [
    '#type' => 'table',
    '#header' => $header,
    '#rows' => $rows,
    '#attributes' => ['id' => 'table-results'],
    '#empty' => t('No results.'),
    '#prefix' => '<div id="ajax-table-results">',
    '#suffix' => '</div>'
  ];

This table is ajaxified and updated when I click on a specific button.

I need to get the output HTML of this table in another function. If I use a dpm($form_state->getValue('table')); I get an empty array. Yet, the other values (of other fields) are accessible in the $form_state.

// My second function
public function secondfunction(array $form, FormStateInterface $form_state) {
  dpm($form_state->getValue('table')); // -> empty value...
  dpm($form_state->getValue('textfield')); // I get a value
}

What do I change in my code to solve this problem?

Answer 1

When you want to get the HTML of the table you must use the renderer service.

In Drupal 8:

$html = \Drupal::service('renderer')->render($form['table']);

Or better, use dependency injection :)

In Drupal 7:

$html = drupal_render($form['table']);