Drupal 7 FAPI - Using Form States for Conditional Field Display
Drupal Form API (FAPI)
Drupal introduced a new form element attribute called 'states'. This adds Javascript to change the state of an element based on another element. The state denotes the property of a form element, for eg. visible, enabled, and so on.
Common states
- enabled
- disabled
- required
- optional
- visible
- invisible
- checked
- unchecked
- expanded
- collapsed
Example
Let us assume that we have a field so-called 'field_user_group' ( list type ) in some form with values gold, silver, bronze and we want to alter the display of field 'field_user_discount' ( text ).
- $form['field_user_discount']['#states'] = array(
- 'disabled' => array(
- ':input[name="field_user_group"]' => array('value' => 'gold'),
- ),
- 'enabled' => array(
- ':input[name="field_user_group"]' => array('value' => 'silver'),
- ),
- 'invisible' => array(
- ':input[name="field_user_group"]' => array('value' => 'bronze'),
- )
The discount field will be disabled when field_user_group has a value of 'gold', enabled when the value is 'silver', and invisible when the value is 'bronze'.
The value might involve even checkbox status like below,
- '#states' => array(
- 'visible' => array(
- ':input[name="field_checkbox_name"]' => array('checked' => TRUE),
- ),