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forms_api_reference.html

Version

1.81.2.4 (checked in on 2008/09/20 at 00:08:52 by heyrocker)

Description

This document provides a programmer's reference to the Drupal Forms API. If you're interested in step-by-step documentation to help you write forms, please see the Forms API QuickStart guide.

Skip to: Properties | Default Values | Elements

Form Controls

Legend:
X = attribute can be used with this type
- = this attribute is not applicable to this type

#type checkbox checkboxes date fieldset file password radio radios select textarea textfield weight
#access X X X X X X X X X X X X
#ahah X - - - - X X - X X X -
#after_build X X X X X X X X X X X X
#attributes X X X X X X X X X X X X
#autocomplete_path - - - - - - - - - - X -
#collapsed - - - X - - - - - - - -
#collapsible - - - X - - - - - - - -
#cols - - - - - - - - - X - -
#default_value X X X - - - X X X X X X
#delta - - - - - - - - - - - X
#description X X X X X X X X X X X X
#disabled X X X - X X X X X X X X
#element_validate X X X X X X X X X X X X
#field_prefix - - - - - - - - - - X -
#field_suffix - - - - - - - - - - X -
#maxlength - - - - - - - - - - X -
#multiple - - - - - - - - X - - -
#options - X - - - - - X X - - -
#parents X X X X X X X X X X X X
#prefix X X X X X X X X X X X X
#required X X X - - X X X X X X X
#return_value X X - - - - X X - - - -
#rows - - - - - - - - - X - -
#size - - - - - - - - X - X -
#suffix X X X X X X X X X X X X
#theme X X X X X X X X X X X X
#title X X X X X X X X X X X X
#tree X X X X X X X X X X X X
#weight X X X X X X X X X X X X

Special Elements

#type button image_button submit form hidden markup item value
#after_build X X X X X X X -
#ahah X X X - - - - -
#action - - - X - - - -
#attributes X X X X X X X -
#button_type X X X - - - - -
#default_value - - - - X - - -
#description - - - - - - X -
#element_validate X X X - X X X X
#executes_submit_callback X X X - - - - -
#method - - - X - - - -
#parents X X X - X - - X
#prefix X X X X X X X -
#redirect - - - X - - - -
#required - - - - X - - -
#src - X - - - - - -
#submit X X X X - - - -
#suffix X X X X X X X -
#theme X X X X X X X -
#title - - - - - - X -
#tree X X X X X - - X
#validate X X X X - - - -
#value X X X - - X X X
#weight X X X - - X X -

Default Values

Every element automatically has these default values (see _element_info):

The following is a list of default values which do not need to be set (found in system_elements):

 

Elements

Note that property names in bold are those that will generally need to be defined when creating this form element. Default values are indicated in parentheses next to property names, if they exist.

button

Description: Format an action button. When the button is pressed, the form will be submitted to Drupal, where it is validated and rebuilt. The submit handler is not invoked.

Properties: #ahah, #attributes, #button_type (default: submit), #executes_submit_callback (default: FALSE), #name (default: op), #prefix, #suffix, #type. #value, #weight

Usage example (node.module):

<?php
$form['preview'] = array(
  '#type' => 'button',
  '#value' => t('Preview'),
  '#weight' => 19,
);
 ?>

checkbox

Description: Format a checkbox.

Properties: #ahah, #attributes, #default_value, #description, #prefix, #required, #return_value (default: 1), #suffix, #title, #type. #weight

Usage example (contact.module):

<?php
$form['copy'] = array(
  '#type' => 'checkbox',
  '#title' => t('Send me a copy.'),
);
?>

checkboxes

Description: Format a set of checkboxes. #options is an associative array, where the key is the #return_value of the checkbox and the value is displayed. The #options array can not have a 0 key, as it would not be possible to discern checked and unchecked states.

Properties: #attributes, #default_value, #description, #options, #prefix, #required, #suffix, #title, #tree (default: TRUE), #type. #weight

Usage example (node.module):

<?php
$form['node_options_'. $node->type] = array(
   '#type' => 'checkboxes',
  '#title' => t('Default options'),
  '#default_value' => variable_get('node_options_'. $node->type, array('status', 'promote')),
   '#options' => array(
    'status' => t('Published'),
    'moderate' => t('In moderation queue'),
    'promote' => t('Promoted to front page'),
    'sticky' => t('Sticky at top of lists'),
    'revision' => t('Create new revision'),
  ),
   '#description' => t('Users with the <em>administer nodes</em> permission will be able to override these options.'),
);
 ?>

date

Description: Format a date selection box. The #default_value will be today's date if no value is supplied. The format for the #default_value and the #return_value is an array with three elements with the keys: 'year', month', and 'day'. For example, array('year' => 2007, 'month' => 2, 'day' => 15)

Properties: #attributes, #default_value, #description, #prefix, #required, #suffix, #title, #type. #weight

Usage example (profile.module):

<?php
$fields[$category][$field->name] = array(
  '#type' => 'date',
  '#title' => check_plain($field->title),
  '#default_value' => $edit[$field->name],
  '#description' => _profile_form_explanation($field),
  '#required' => $field->required
);
?>

fieldset

Description: Format a group of form items.

Properties: #attributes, #collapsed (default: FALSE), #collapsible (default: FALSE), #description, #prefix, #suffix, #title, #type. #weight

Usage example (contact.module):

<?php
$form['contact'] = array(
  '#type' => 'fieldset',
  '#title' => t('Contact settings'),
  '#weight' => 5,
  '#collapsible' => TRUE,
  '#collapsed' => FALSE,
);
?>

file

Description: Format a file upload field.

Note: you will need to include $form['#attributes'] = array('enctype' => "multipart/form-data"); in your form. See this handbook page for an example http://drupal.org/node/111782.

Note: the #required property is not supported (setting it to true will always cause a validation error). Instead, you may want to use your own validation function to do checks on the $_FILES array with #required set to false. You will also have to add your own required asterisk if you would like one.

Properties: #attributes, #description, #prefix, #size (default: 60), #suffix, #title, #type. #weight

Usage example (upload.module):

<?php
$form['new']['upload'] = array(
  '#type' => 'file',
  '#title' => t('Attach new file'),
  '#size' => 40,
);
?>

form

Description: A form containing form elements

Properties: #action (default: request_uri()), #attributes, #method (default: 'post'), #prefix, #submit, #suffix, #theme, #validate

Usage example:

N/A

hidden

Description: Store data in a hidden form field.

Properties: #prefix, #suffix, #type, #value

Usage example (block.module):

<?php
$form['bid'] = array('#type' => 'hidden', '#value' => $bid);
?>

image_button

Description: Format a form submit button with an image.

Properties: #ahah, #attributes, #button_type (default: 'submit'), #executes_submit_callback (default: TRUE), #name (default: 'op'), #prefix, #src, #suffix, #submit, #type. #value, #weight

markup

Description: Generate generic markup for display inside forms. Note that there is no need to declare a form element as #type = 'markup', as this is the default type.

Note: if you use markup, if your content is not wrapped in tags (generally <p> or <div>), your content will fall outside of collapsed fieldsets.

Properties: #attributes, #prefix (default: ''), #suffix (default: ''), #type. #value, #weight

Usage example (contact.module):

<?php
$form['contact_information'] = array(
  '#value' => variable_get('contact_form_information', t('You can leave us a message using the contact form below.')),
);
?>

item

Description: Generate a display-only form element allowing for an optional title and description.

Note: since this is a read-only field, setting the #required property will do nothing except theme the form element to look as if it were actually required (i.e. by placing a red star next to the #title).

Properties: #attributes, #description, #prefix (default: ''), #required, #suffix (default: ''), #title, #type, #value, #weight

Usage example (contact.module):

<?php
 $form['from'] = array(
  '#type' => 'item',
  '#title' => t('From'),
  '#value' => $user->name .' &lt;'. $user->mail .'&gt;',
);
 ?>

password

Description: Format a single-line text field that does not display its contents visibly.

Properties: #ahah, #attributes, #description, #maxlength (default: 30), #prefix, #required, #size (default: 64), #suffix, #title, #type. #weight

Usage example (user.module):

<?php
$form['pass'] = array(
  '#type' => 'password',
  '#title' => t('Password'),
  '#maxlength' => 64,
  '#size' => 15,
);
?>

radio

Description: Format a radio button.

Properties: #ahah, #attributes, #default_value, #description, #prefix, #required, #suffix, #title, #type. #weight

Usage example:

N/A

radios

Description: Format a set of radio buttons.

Properties: #attributes, #default_value, #description, #options, #prefix, #required, #suffix, #title, #type. #weight

Usage example (comment.module):

<?php
$form['posting_settings']['comment_preview'] = array(
  '#type' => 'radios',
  '#title' => t('Preview comment'),
  '#default_value' => variable_get('comment_preview', 1),
  '#options' => array(t('Optional'), t('Required')),
);
?>

select

Description: Format a drop-down menu or scrolling selection box.

Properties: #ahah, #attributes, #default_value, #description, #multiple, #options, #prefix, #required, #suffix, #title, #type. #weight

Usage example (system.module):

<?php
$form['feed']['feed_item_length'] = array(
   '#type' => 'select',
  '#title' => t('Display of XML feed items'),
  '#default_value' => variable_get('feed_item_length','teaser'),
   '#options' => array(
    'title' => t('Titles only'),
    'teaser' => t('Titles plus teaser'),
    'fulltext' => t('Full text'),
  ),
   '#description' => t('Global setting for the length of XML feed items that are output by default.'),
);
?>

submit

Description: Format a form submit button.

Properties: #ahah, #attributes, #button_type (default: 'submit'), #executes_submit_callback (default: TRUE), #name (default: 'op'), #prefix, #suffix, #type. #value, #weight

Usage example (locale.module):

<?php
$form['submit'] = array('#type' => 'submit', '#value' => t('Import'));
?>

textarea

Description: Format a multiple-line text field.

Properties: #ahah, #attributes, #cols (default: 60), #default_value, #description, #prefix, #required, #suffix, #title, #type. #rows (default: 5), #weight

Usage example (forum.module):

<?php
$form['body'] = array(
  '#type' => 'textarea',
  '#title' => t('Body'),
  '#default_value' => $node->body,
  '#required' => TRUE
);
 ?>

textfield

Description: Format a single-line text field.

Properties: #ahah, #attributes, #autocomplete_path (default: FALSE), #default_value, #description, #field_prefix, #field_suffix, #maxlength (default: 128), #prefix, #required, #size (default: 60), #suffix, #title, #type. #weight

Usage example (forum.module):

<?php
$form['title'] = array(
  '#type' => 'textfield',
  '#title' => t('Subject'),
  '#default_value' => $node->title,
  '#size' => 60,
  '#maxlength' => 128,
  '#required' => TRUE,
);
?>

value

Description: A form value that is internal to the form and never displayed to the screen.

Properties: #type, #value

Usage example (node.module):

<?php
$form['vid'] = array('#type' => 'value', '#value' => $node->vid);
?>

weight

Description: Format a weight selection menu.

Properties: #attributes, #delta (default: 10), #default_value, #description, #prefix, #required, #suffix, #title, #type. #weight

Usage example (menu.module):

<?php
$form['weight'] = array(
  '#type' => 'weight',
  '#title' => t('Weight'),
  '#default_value' => $edit['weight'],
  '#delta' => 10,
  '#description' => t('Optional. In the menu, the heavier items will sink and the lighter items will be positioned nearer the top.'),
);
?>

Properties

#access

Description: Whether the element is accessible or not, when FALSE, the element is not rendered and the user submitted value is not taken into consideration.

Values: TRUE or FALSE.

#action

Used by: form

Description: The path to which the form will be submitted.

Values: An internal path

Usage example (comment.module):

<?php
$form['#action'] = url('comment/reply/'. $edit['nid']);
 ?>

Do not forget the # before property names.

#after_build

An array of function names which will be called after the form is built. Example: node preview.

Usage example (system.module):

<?php
$form['files']['file_directory_path'] = array(
   '#type' => 'textfield',
   '#title' => t('File system path'),
   '#default_value' => file_directory_path(),
   '#maxlength' => 255,
   '#description' => t('A file system path where the files will be stored. This directory has to exist and be writable by Drupal. If the download method is set to public this directory has to be relative to Drupal installation directory, and be accessible over the web. When download method is set to private this directory should not be accessible over the web. Changing this location after the site has been in use will cause problems so only change this setting on an existing site if you know what you are doing.'),
);
$form['#after_build'] = array('system_check_directory');

...

function system_check_directory($form, $form_element) {
   file_check_directory($form_element['#value'], FILE_CREATE_DIRECTORY, $form_element['#parents'][0]);
   return $form_element;
}
 ?>

Property names without # signs causes havoc.

#ahah

Used by: button, checkbox, image button, password, radio, select, submit, textarea, textfield

An array of elements whose values control the behavior of the element with respect to the Drupal AHAH javascript methods.

The #ahah name refers to AHAH javascript replacement (Asychronous HTML and HTTP), a relative of AJAX. AHAH is a form of javascript page replacement that is both easy and straight forward. In a nutshell an AHAH request follows these steps:

  1. Drupal builds a form element with a set of #ahah properties. The misc/ahah.js file is included on the page automatically.
  2. ahah.js finds all the form elements on the page that have an #ahah['path'] set and adds an event handler for the #ahah['event'] set on that form element.
  3. When the #ahah['event'] occurs on the element (such as 'click'), the AHAH request is made to the Drupal path of the element's #ahah['path'].
  4. Drupal generates HTML in a second request in the background. While the user waits for the callback to execute a throbber or progress bar is shown as determined by #ahah['progress']. The result is returned to the original page containing the form element.
  5. ahah.js gets the result and inserts the returned HTML into the #ahah['wrapper']. Depending on the #ahah['method'], the result may affect the wrapper in different ways.

#ahah['effect']

Description: Specifies the effect used when adding the content from an AHAH request.

Values: String. Possible values: 'none' (default), 'fade', 'slide'. If the interface elements library is installed, any effect with the name effectToggle may also be used.

Usage example (poll.module):

  $form['choice_wrapper']['poll_more'] = array(
    '#type' => 'submit',
    '#value' => t('More choices'),
    '#description' => t("If the amount of boxes above isn't enough, click here to add more choices."),
    '#weight' => 1,
    '#submit' => array('poll_more_choices_submit'), // If no javascript action.
    '#ahah' => array(
      'path' => 'poll/js',
      'wrapper' => 'poll-choices',
      'method' => 'replace',
      'effect' => 'fade',
    ),

#ahah['event']

Description: When this event occurs to this element, Drupal will perform an HTTP request in the background via Javascript.

Values: String. Possible values: 'click', 'blur', 'change'. Note that #ahah['event'] does not need to be explicitly specified. Although it can be manually set, usually the default value will be sufficient.

#ahah['method']

Description: Modify the behavior of the returned HTML from an AHAH request when inserting into the #ahah_wrapper. If not set, the returned HTML will replace the contents of the wrapper element, but it's also possible to use any of the available jQuery operations for DOM manipulation.

Values: String. Possible values: 'replace' (default), 'after', 'append', 'before', 'prepend'.

#ahah['path']

Description: If set, this property triggers AHAH behaviors on a form element. This is the Drupal menu path to a callback function which will generate HTML and return the string of HTML to Drupal. The result will be placed in the div specified in #ahah['wrapper'].

Values: String containing a Drupal menu path.

Usage example (upload.module):

<?php
/**
* Implementation of hook_menu().
*/
function upload_menu() {
  $items['upload/js'] = array(
    'page callback' => 'upload_js',
    'access arguments' => array('upload files'),
    'type' => MENU_CALLBACK,
  );
  ...
  return $items;
}

...

function _upload_form($node) {
  ...
    $form['new']['attach'] = array(
      '#type' => 'submit',
      '#value' => t('Attach'),
      '#name' => 'attach',
      '#ahah' => array(
        'path' => 'upload/js',
        'wrapper' => 'attach-wrapper',
        'progress' => array('type' => 'bar', 'message' => t('Please wait...')),
      ),
      '#submit' => array('node_form_submit_build_node'),
    );
  ...
return $form;
?>

#ahah['path'] is set to 'upload/js', which has a menu item defined in the same module. Then the menu hook will call the 'upload_js' function which generates HTML and returns it to original page.

#ahah['progress']

Description: Choose either a throbber or progress bar that is displayed while awaiting a response from the callback, and add an optional message.

Values: Array.

Possible keys: 'type', 'message', 'url', 'interval'

Possible values:

  • #ahah['progress']['type'] String. Possible values: 'throbber' (default), 'bar'.
  • #ahah['progress']['message'] String. An optional message to the user; should be wrapped with t().
  • #ahah['progress']['url'] String. The optional callback path to use to determine how full the progress bar is (as defined in progress.js). Only useable when 'type' is 'progress'.
  • #ahah['progress']['interval'] String. The iterval to be used in updating the progress bar (as defined in progress.js). Ony used if 'url' is defined and 'type' is 'progress'.

Usage example: see above useage in upload.module

#ahah['wrapper']

Description: This property defines the HTML id attribute of an element on the page will server as the destination for HTML returned by an AHAH request. Usually, a div element is used as the wrapper, as it provides the most flexibility for placement of elements before, after, or inside of it's HTML tags. This property is required for using AHAH requests in on a form element.

Values: String containg a valid id attribute of an HTML element on the same page.

Usage example (upload.module):

    $form['new']['attach'] = array(
      '#type' => 'submit',
      '#value' => t('Attach'),
      '#name' => 'attach',
      '#ahah' => array(
        'path' => 'upload/js',
        'wrapper' => 'attach-wrapper',
        'progress' => array('type' => 'bar', 'message' => t('Please wait...')),
      ),
      '#submit' => array('node_form_submit_build_node'),
    );

#attributes

Used by: button, checkbox, checkboxes, date, fieldset, file, form, markup, password, radio, radios, select, submit, textarea, textfield, weight

Description: Additional HTML attributes, such as 'class' can be set using this mechanism.

Values: Any HTML attribute not covered by other properties, e.g. class (for control types), enctype (for forms).

Usage example (search.module):

<?php
$form['#attributes'] = array('class' => 'search-form');
?>

The # is mandatory before property names.

#autocomplete_path

Used by: textfield

Description: The path the AJAX autocomplete script uses as the source for autocompletion.

Usage example (node.module):

<?php
$form['author']['name'] = array(
  '#type' => 'textfield',
  '#title' => t('Authored by'),
  '#maxlength' => 60,
  '#autocomplete_path' => 'user/autocomplete',
  '#default_value' => $node->name,
  '#weight' => -1,
);
?>

It's very important that you do not forget the # before property names.

#built

Used by: form

Description: Used to ascertain whether or not a form element has been built yet.

Values: TRUE or FALSE

Usage example: INTERNAL. See the _form_builder function in form.inc.

The first character of property names is #.

#button_type

Used by: button, submit

Description: Indicates CSS class to use for button(form-button_type)

Values: submit, ???

Usage example: (system.module):

<?php
$type['submit'] = array(
  '#input' => TRUE,
  '#name' => 'op',
  '#button_type' => 'submit',
  '#submit' => TRUE,
);
?>

Developers should take care to not forget the first # character in property names.

#collapsed

Used by: fieldset

Description: Indicates whether or not the fieldset is collapsed by default. See #collapsible property.

Values: TRUE or FALSE

Usage example (block.module) :

<?php
$form['block'] = array(
  '#type' => 'fieldset',
  '#title' => t('Block configuration'),
  '#weight' => 3,
  '#collapsible' => TRUE,
  '#collapsed' => FALSE,
  '#tree' => TRUE,
);
?>

Child names do not have a # as first char, but property names do.

#collapsible

Used by: fieldset

Description: Indicates whether or not the fieldset can be collapsed with JavaScript. See #collapsed property.

Values: TRUE or FALSE

Usage example (block.module):

<?php
$form['block'] = array(
  '#type' => 'fieldset',
  '#title' => t('Block configuration'),
  '#weight' => 3,
  '#collapsible' => TRUE,
  '#collapsed' => FALSE,
  '#tree' => TRUE,
);
?>

One of the most important things about form API is not forgetting the # where it's appropriate.

#cols

Used by: textarea

Description: How many columns wide the textarea should be (see also #rows)

Values: A positive number

Usage example (aggregator.module):

<?php
$form['description'] = array(
  '#type' => 'textarea',
  '#title' => t('Description'),
  '#default_value' => $edit['description'],
  '#cols' => 60,
  '#rows' => 5,
);
?>

The first # lets form API decide between a property name and a child.

#default_value

Used by: button, checkbox, checkboxes, date, file, markup, password, radio, radios, select, submit, textarea, textfield, weight

Description: The value of the form element that will be displayed or selected initially if the form has not been submitted yet. Should NOT be confused with #value, which is a hard-coded value the user cannot change!

Values: Mixed

Usage example (forum.module):

<?php
$form['body'] = array(
  '#type' => 'textarea',
  '#title' => t('Body'),
  '#default_value' => $node->body,
  '#required' => TRUE,
);
?>

How many different forms of warnings can I figure out to tell you that the first # in property names are important?

#delta

Used by: weight

Description: Number of weights to have selectable. For example, with $delta => 10, the weight selection box would display numbers from -10 to 10.

Values: A positive number

Usage example (menu.module):

<?php
$form['weight'] = array(
  '#type' => 'weight',
  '#title' => t('Weight'),
  '#default_value' => $edit['weight'],
  '#delta' => 10,
  '#description' => t('Optional. In the menu, the heavier items will sink and the lighter items will be positioned nearer the top.'),
);
?>

One of the most common errors for 4.7 is leaving out the # in the beginning of property names.

#description

Used by: checkbox, checkboxes, date, fieldset, file, markup, password, radio, radios, select, textarea, textfield, weight

Description: The description of the form element. Make sure to enclose inside the t() function so this property can be translated.

Values: Mixed

Usage example (menu.module):

<?php
$form['weight'] = array(
  '#type' => 'weight',
  '#title' => t('Weight'),
  '#default_value' => $edit['weight'],
  '#delta' => 10,
  '#description' => t('Optional. In the menu, the heavier items will sink and the lighter items will be positioned nearer the top.'),
);
?>

#disabled

Used by: checkbox, checkboxes, date, file, password, radio, radios, select, textarea, textfield, weight

Description: Disables (greys out) a form input element.

Values: TRUE or FALSE

Usage example (system.module):

<?php
      if (isset($disabled[$name])) {
        $form['theme_settings'][$name]['#disabled'] = TRUE;
      }
?>

It can not be stressed enough that property names begin with a #.

#element_validate

Used by: any element

Description: A list of custom validation functions that need to be passed. The functions must use form_error() or form_set_error() to set an error if the validation fails.

Values: an array of function names to be called to validate this element (and/or its children).

A validation function for an element takes the element and the form state as parameters, and has the form:

function myelement_validate($element, &$form_state) {
   if (empty($element['#value']) {
     form_error($element, t('This field is required.'));
   }
}

Usage example (filter.module):

<?php
  if (count($formats) > 1) {
    $form = array(
      '#type' => 'fieldset',
      '#title' => t('Input format'),
      '#collapsible' => TRUE,
      '#collapsed' => TRUE,
      '#weight' => $weight,
      '#element_validate' => array('filter_form_validate'),
    );
   ...
?>

While #element_validate makes sure that user data is valid, nothing validates the form for missing # in the beginning of property name.

#error

INTERNAL. Indicates whether or not a form element has been flagged as having an error.

#executes_submit_callback

Used by: button, submit, image_button

Description: Indicates whether or not button should submit the form.

Values: TRUE or FALSE

#id

INTERNAL. Used to populate form elements' id property.

#input

INTERNAL. Indicates whether or not input is possible for this form element.

#field_prefix

Used by: textfield

Description: Text or code that is placed directly in front of the textfield. This can be used to prefix a textfield with a constant string.

Values: Mixed

Usage example (system.module):

<?php
$form['site_403'] = array(
  '#type' => 'textfield',
  '#title' => t('Default 403 (access denied) page'),
  '#default_value' => variable_get('site_403', ''),
  '#size' => 40,
  '#description' => t('This page is displayed when the requested document is denied to the current user. If unsure, specify nothing.'),
  '#field_prefix' => url(NULL, NULL, NULL, TRUE) . (variable_get('clean_url', 0) ? '' : '?q=')
);
?>

#field_suffix

Used by: textfield

Description: Text or code that is placed directly after a textfield. This can be used to add a unit to a textfield.

Values: Mixed

Usage example (system.module):

<?php
$form[