Single element

A single element repeats one input. The submitted value is a flat list of strings.

Default text field

Without #element, each row is a text field.

$form['tags'] = [
  '#type' => 'element_multiple',
  '#title' => $this->t('Tags'),
  '#default_value' => ['One', 'Two', 'Three'],
];

The value is ['One', 'Two', 'Three']. The empty fourth row is dropped.

Another input type

Set #element to any input element. Use #title_display => 'invisible' so the title does not repeat in every row.

$form['emails'] = [
  '#type' => 'element_multiple',
  '#title' => $this->t('Email addresses'),
  '#element' => [
    '#type' => 'email',
    '#title' => $this->t('Email address'),
    '#title_display' => 'invisible',
    '#placeholder' => $this->t('name@example.com'),
  ],
  '#default_value' => ['example@example.com'],
];

Add a row after a given row

The plus button of a row adds a blank row right after it. The page does not reload.

Notes

• Blank rows are dropped from the value.
• To show a column title, set #header to TRUE. See Composite with header.
• Related properties: #element, #default_value.