Composite with header

#header turns a composite element into a real table with one column per child. It also controls the header row. Every example below uses the same two children.

$children = [
  'textfield' => [
    '#type' => 'textfield',
    '#title' => $this->t('Name'),
  ],
  'email' => [
    '#type' => 'email',
    '#title' => $this->t('Email'),
  ],
];

No header

Without #header, one header cell spans the table and the children share one cell per row.

$form['contacts'] = [
  '#type' => 'element_multiple',
  '#title' => $this->t('Contacts'),
  '#element' => $children,
];

#header => TRUE

One column per visible child. The column title is the #title of the child. The titles are hidden inside the cells.

$form['contacts'] = [
  '#type' => 'element_multiple',
  '#title' => $this->t('Contacts'),
  '#header' => TRUE,
  '#element' => $children,
];

#header as a string

A single header cell spans all columns.

$form['contacts'] = [
  '#type' => 'element_multiple',
  '#title' => $this->t('Contacts'),
  '#header' => $this->t('Header text'),
  '#element' => $children,
];

#header as an array

Give one entry per visible child. An entry is a string or a header cell array, for example ['data' => $this->t('Full name'), 'width' => '30%'] to size the column.

$form['contacts'] = [
  '#type' => 'element_multiple',
  '#title' => $this->t('Contacts'),
  '#header' => [
    $this->t('Full name'),
    $this->t('Email address'),
  ],
  '#element' => $children,
];

#header_label

A single header cell with your text, spanning all columns.

$form['contacts'] = [
  '#type' => 'element_multiple',
  '#title' => $this->t('Contacts'),
  '#header' => TRUE,
  '#header_label' => $this->t('Header label'),
  '#element' => $children,
];

Notes

• Children that are hidden do not get a column. See Hidden and server-only children.
• For a single element, #header => TRUE gives one column titled with the #title of #element.
• Related properties: #header, #header_label.