Form API Reference

This document provides a programmer's reference to the Drupal Form API. For a brief introduction on how to create forms, see the Form generation guide. For more extensive information about the Form API, see the Form API handbook.

Skip to: Properties | Default Values | Elements

Note that internal properties are not included in the table below, but are included in the Properties list. These include: #built, #children, #error, #id, #input, #printed, #validation_arguments

Form Controls

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

Default Values

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

• #description = NULL
• #attributes = array()
• #required = FALSE
• #tree = FALSE
• #parents = array()

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

• button
  • #name = 'op'
  • #button_type = 'submit'
  • #executes_submit_callback = FALSE
  • #ajax['event'] = 'mousedown'
• checkbox
  • #return_value = 1
  • #ajax['event'] = 'change'
  • #title_display = 'after'
• checkboxes
  • #tree = TRUE
• fieldset
  • #collapsible = FALSE
  • #collapsed = FALSE
• file
  • #size = 60
• form
• • #method = 'post'
  • #action = request_uri()
• image_button
  • #button_type = 'submit'
  • #executes_submit_callback = TRUE
  • #ajax['event'] = 'mousedown'
• radio
• • #ajax['event'] = 'change'
  • #title_display = 'after'
• password
• • #size = 60
  • #maxlength = 128
  • #ajax['event'] = 'blur'
• password_confirm
• • #size = 60
• submit
• • #name = 'op'
  • #button_type = 'submit'
  • #executes_submit_callback = TRUE
  • #ajax['event'] = 'mousedown'
• textarea
  • #cols = 60
  • #resizable = TRUE
  • #rows = 5
  • #ajax['event'] = 'blur'
• textfield
• • #size = 60
  • #maxlength = 128
  • #autocomplete_path = FALSE
  • #ajax['event'] = 'blur'
• weight
  • #delta = 10

 

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.

actions

Description: A wrapper element to group one or more buttons in a form. Use of the 'actions' element as an array key helps to ensure proper styling in themes and to enable other modules to properly alter a form's actions.

Properties: #access, #after_build, #attributes #children, #id, #parents, #post_render, #pre_render, #prefix, #process, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #weight

Usage example:

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: #access, #after_build, #ajax, #attributes, #button_type (default: submit), #disabled, #element_validate, #executes_submit_callback (default: FALSE), #limit_validation_errors, #name (default: op), #parents, #post_render, #prefix, #pre_render, #process, #submit, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #validate, #value, #weight

Usage example (node.module):

checkbox

Description: Format a checkbox.

Properties: #access, #after_build, #ajax, #attributes, #default_value, #description, #disabled, #element_validate, #field_prefix, #field_suffix, #parents, #post_render, #prefix, #pre_render, #process, #required, #return_value (default: 1), #states, #suffix, #theme, #theme_wrappers, #title, #title_display (default: after), #tree, #type, #weight

Usage example (contact.module):

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 cannot have a 0 key, as it would not be possible to discern checked and unchecked states.

Properties: #access, #after_build, #ajax, #attributes, #default_value, #description, #disabled, #element_validate, #options, #parents, #post_render, #prefix, #pre_render, #process, #required, #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree (default: TRUE), #type, #weight

Usage example (form_example_states.inc):

container

Description: Returns HTML to wrap child elements in a container. Surrounds child elements with a <div> and adds attributes such as classes or an HTML id.

Properties: #access, #after_build, #attributes #children, #id, #parents, #post_render, #pre_render, #prefix, #process, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #weight

Usage example (field.form.inc):

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: #access, #after_build, #attributes, #default_value, #description, #disabled, #element_validate, #parents, #post_render, #prefix, #pre_render, #process, #required, #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (profile.module):

fieldset

Description: Format a group of form items.

Properties: #access, #after_build, #attributes, #collapsed (default: FALSE), #collapsible (default: FALSE), #description, #element_validate, #parents, #post_render, #prefix, #pre_render, #process, #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (contact.module):

file

Description: Format a file upload field.

Note: Drupal will add the code enctype="multipart/form-data", required by browsers to handle files, so it's not necessary to include it yourself.

Properties: #access, #after_build, #array_parents, #attached, #attributes, #description, #disabled, #element_validate, #parents, #post_render, #prefix, #pre_render, #process, #required, #size (default: 60), #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (file.module):

form

Description: A form containing form elements

Properties: #access, #action (default: request_uri()), #after_build, #attributes, #method (default: 'post'), #post_render, #prefix, #pre_render, #process, #submit, #states, #suffix, #theme, #theme_wrappers, #tree, #validate

Usage example:

N/A

hidden

Description: Store data in a hidden form field.

Properties: #access, #after_build, #default_value, #element_validate, #parents, #post_render, #prefix, #pre_render, #process, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #value, #weight

Usage example (block.module):

Note that if you plan to use JavaScript to change your hidden element's value, you will need to use the #default_value property rather than #value.

image_button

Description: Format a form submit button with an image.

Properties: #access, #after_build, #ajax, #attributes, #button_type (default: 'submit'), #disabled, #element_validate, #executes_submit_callback (default: TRUE), #limit_validation_errors, #parents, #post_render, #prefix, #pre_render, #process, #return_value (default: TRUE), #src, #submit, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #validate, #value, #weight

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: #access, #after_build, #description, #element_validate, #markup, #parents, #post_render, #prefix, #pre_render, #process, #required, #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (contact.module):

machine_name

Description: Format a single-line text field to store a unique machine-readable name.

Provides a form element to enter a machine name, which is validated to ensure that the name is unique and does not contain disallowed characters. All disallowed characters are replaced with a replacement character via JavaScript.

The element validation checks that the submitted value

• does not contain the replacement character only
• does not contain disallowed characters
• is unique; i.e., does not already exist
• does not exceed the maximum length (via #maxlength)
• cannot be changed after creation (via #disabled)

Non-standard form element properties:

• #machine_name: (array)
  • exists: A function name to invoke for checking whether a submitted machine name value already exists. The submitted value is passed as argument. In most cases, an existing API or menu argument function can be re-used. The callback is only invoked, if the submitted value differs from the element's #default_value
  • source: (optional) The #array_parents of the form element containing the human-readable name (i.e., as contained in the $form structure) to use as source for the machine name. Defaults to array('name').
  • label: (optional) A text to display as label for the machine name value after the human-readable name form element. Defaults to "Machine name".
  • replace_pattern: (optional) A regular expression (without delimiters) matching disallowed characters in the machine name. Defaults to '[^a-z0-9_]+'.
  • replace: (optional) A character to replace disallowed characters in the machine name via JavaScript. Defaults to '_' (underscore). When using a different character, 'replace_pattern' needs to be set accordingly.

Properties: #access, #after_build, #ajax, #attributes, #autocomplete_path (default: FALSE), #default_value, #description (default: 'A unique machine-readable name. Can only contain lowercase letters, numbers, and underscores.'), #disabled, #element_validate, #field_prefix, #field_suffix, #maxlength (default: 64), #parents, #post_render, #prefix, #pre_render, #process, #required (default: TRUE), #size (default: 60), #states, #suffix, #theme (default: 'textfield'), #theme_wrappers (default: 'form_element'), #title (default: 'Machine-readable name'), #title_display #tree, #type, #weight

Usage example (taxonomy.admin.inc):

Usage example (menu.admin.inc):

managed_file

Description: Provides a complete ajax/progress aware widget for uploading a file and saving it to the {file_managed} table.

By default a simple upload button is provided for choosing the file to upload. Once a file has been chosen it can be explicitly uploaded via the "Upload" button. The upload is via AJAX and a progress meter is displayed. The form's validate and submit handlers receive a file object ID in $form_state['values'] that represents the ID of the new file in the {file_managed} table.

The #managed_file element is expanded into a set of FAPI elements including two '#submit' buttons one for Upload one for Remove, a '#file' element and a handful of '#hidden' and '#markup' elements to handle progress indication and displaying of already uploaded files.

Note: New files are uploaded with a status of 0 and are treated as temporary files which are removed after 6 hours via cron. Your module is responsible for changing the $file objects status to FILE_STATUS_PERMANENT and saving the new status to the database. Something like the following within your submit handler should do the trick.

(Without the call to file_usage_add, file_managed_file_validate produces an error upon saving the form, saying that the uploaded file may not be referenced.)

Once a file has been uploaded the file object's fid can be used as the #default_value for the form element. This will display an icon, a link to the file, and a remove button.

Clicking the remove button sets the value of the field to 0 and your module is responsible for actually removing the file from the files table and the file system using file_delete().

Non-standard form element properties:

• #progress_indicator: options are 'none', 'bar', and 'throbber', default is 'throbber'.
• #progress_message: (string) Progress message to display along with progress meter while a file is being uploaded. Defaults to NULL.
• #upload_validators: (array) an array of callback functions to perform validation of uploaded files.
• #upload_location (string) location on server where uploaded files should be stored. e.g.) 'public://files/my_files_director'

Properties: #access, #after_build, #array_parents, #attached, #attributes, #description, #disabled, #element_validate, #parents, #post_render, #prefix, #pre_render, #process, #states, #suffix, #theme, #theme_wrappers, #title, #tree, #weight

Usage example (image_example.pages.inc.):

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: #access, #after_build, #element_validate, #markup, #parents, #post_render, #prefix, #pre_render, #process, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #weight

Usage example (contact.module):

password

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

Properties: #access, #after_build, #ajax, #attributes, #description, #disabled, #element_validate, #field_prefix, #field_suffix, #maxlength (default: 128), #parents, #post_render, #prefix, #pre_render, #process, #required, #size (default: 60), #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (user.module):

password_confirm

Description: Format a pair of password fields, which do not validate unless the two entered passwords match.

Properties: #access, #after_build, #description, #disabled, #element_validate, #field_prefix, #field_suffix, #parents, #post_render, #prefix, #pre_render, #process, #required, #size (default: 60), #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (user.module):

radio

Description: Format a radio button.

Properties: #access, #after_build, #ajax, #attributes, #default_value, #description, #disabled, #element_validate, #field_prefix, #field_suffix, #parents, #post_render, #prefix, #pre_render, #process, #required, #return_value, #states, #suffix, #theme, #theme_wrappers, #title, #title_display (default: after), #tree, #type, #weight

Usage example:

N/A

radios

Description: Format a set of radio buttons.

Properties: #access, #after_build, #ajax, #attributes, #default_value, #description, #disabled, #element_validate, #options, #parents, #post_render, #prefix, #pre_render, #process, #required, #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (poll.module):

select

Description: Format a drop-down menu or scrolling selection box. See #empty_option and #empty_value for an explanation of various settings for a select element, including behavior if #required is TRUE or FALSE.

Properties: #access, #after_build, #ajax, #attributes, #default_value, #description, #disabled, #element_validate, #empty_option, #empty_value, #field_prefix, #field_suffix, #multiple, #options, #parents, #post_render, #prefix, #pre_render, #process, #required, #size, #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (contact.admin.inc):

submit

Description: Format a form submit button.

Properties: #access, #after_build, #ajax, #attributes, #button_type (default: 'submit'), #disabled, #element_validate, #executes_submit_callback (default: TRUE), #limit_validation_errors, #name (default: 'op'), #parents, #post_render, #prefix, #pre_render, #process, #submit, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #validate, #value, #weight

Usage example (locale.module):

tableselect

Description: A table created with a far left column of radios or checkboxes. Build the table headings and columns with the #headers property, and the rows with the #options property. See Adding checkboxes to a table for a full explanation.

Other settings:

• To set accessibility tags for the radios or checkboxes, build one of the cells in the #options property using the 'title' => array( 'data' => array(#title => 'mytitle'))) construction, as in the $options variable in the usage example below. Drupal will create invisible label tags for the left column based on this value.
• To disable the default "check all" button for the checkboxes, set #js_select property to FALSE. This is FALSE by default for radios.
• Setting #multiple to TRUE will give you checkboxes instead of radios.

Properties: #access, #after_build, #ajax, #attributes, #default_value, #element_validate, #empty, #header, #js_select, #multiple, #options, #parents, #post_render, #prefix, #pre_render, #process, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #weight

Usage example (node.admin.inc):

text_format

Description: A text-format-enabled version of a textarea.

Properties: #access, #after_build, #ajax, #attributes, #cols (default: 60), #default_value, #description, #disabled, #element_validate, #parents, #post_render, #prefix, #pre_render, #process, #required, #resizable (default: TRUE), #rows (default: 5), #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree,#type, #weight

Non-standard Properties:

• #format: the format to apply. If you want to use the default format, set this property to NULL in your form constructor function, and the filter system will handle the rest.
• #base_type (optional): defaults to 'textarea'. This makes it possible to also attach the text format selector to other form element types, such as textfields.

Usage example (taxonomy.admin.inc):

textarea

Description: Format a multiple-line text field.

Properties: #access, #after_build, #ajax, #attributes, #cols (default: 60), #default_value, #description, #disabled, #element_validate, #field_prefix, #field_suffix, #parents, #post_render, #prefix, #pre_render, #process, #required, #resizable (default: TRUE), #rows (default: 5), #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (comment.module):

textfield

Description: Format a single-line text field.

Properties: #access, #after_build, #ajax, #attributes, #autocomplete_path (default: FALSE), #default_value, #description, #disabled, #element_validate, #field_prefix, #field_suffix, #maxlength (default: 128), #parents, #post_render, #prefix, #pre_render, #process, #required, #size (default: 60), #states, #suffix, #text_format, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (forum.module):

token

Description: Store token data in a hidden form field (generally used to protect against cross-site forgeries). A token element is automatically added to each Drupal form by drupal_prepare_form(), so you don't generally have to add one yourself.

Properties: #access, #after_build, #default_value, #element_validate, #parents, #post_render, #prefix, #pre_render, #process, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #value, #weight

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);
?>

Note that as of Drupal 6, you can also simply store arbitrary variables in $form['#foo'] instead, as long as '#foo' does not conflict with any other internal property of the Form API.

vertical_tabs

Description: Formats all child fieldsets and all non-child fieldsets whose #group is assigned this element's name as vertical tabs.

Properties: #access, #after_build, #default_tab, #element_validate, #parents, #post_render, #prefix, #pre_render, #process, #states, #suffix, #theme, #theme_wrappers, #tree, #type, #weight

Functions that use vertical_tabs:
block_admin_configure in block.admin.inc
user_admin_settings in user.admin.inc

weight

Description: Format a weight selection menu.

Properties: #access, #after_build, #attributes, #default_value, #delta (default: 10), #description, #disabled, #element_validate, #parents, #post_render, #prefix, #pre_render, #process, #required, #states, #suffix, #theme, #theme_wrappers, #title, #title_display, #tree, #type, #weight

Usage example (menu.module):

Properties

#access

Used by: All elements and forms

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):

#after_build

Used by: All elements and forms

Description: An array of function names which will be called after the form or element is built.

Usage example (system.admin.inc):

#ajax

Used by: button, checkbox, checkboxes, image button, password, radio, radios, select, submit, tableselect, textarea, text_format, textfield

An array of elements whose values control the behavior of the element with respect to the Drupal AJAX framework.

AJAX (Asynchronous Javascript and XML) is a term used for dynamic communication between the browser and the server, without page reloads. A purist would insist that the Drupal technique is AHAH (Asychronous HTML and HTTP) because XML is not used. Until Drupal 7, AJAX was known as AHAH. In a nutshell an AJAX request follows these steps:

1. Drupal builds a form element with a set of #ajax properties. The misc/ajax.js file is included on the page automatically.
2. ajax.js finds all the form elements on the page that have an #ajax['callback'] or an #ajax['path'] set and adds an event handler for the #ajax['event'] set on that form element.
3. When the #ajax['event'] occurs on the element (such as 'click'), the AJAX request is made to the Drupal path of the element's #ajax['path']. If an #ajax['callback'] has been specified (the normal case), the Drupal path will be system/ajax.
4. Form information gets processed, and the function specified in #ajax['callback'] is called.  #ajax['callback'] can return either HTML, a renderable array, or an array of AJAX commands.
5. While the user waits for the callback to execute a throbber or progress bar is shown as determined by #ajax['progress']. The result is returned to the original page containing the form element.
6. ajax.js gets the result. If it is HTML and #ajax['wrapper'] is set, the HTML replaces the element specified by #ajax['wrapper']. If it is an array of AJAX commands, the commands are executed. and inserts the returned HTML into the #ajax['wrapper']. 

Example usages of basic AJAX and AJAX commands are provided in the Examples module.

#ajax['callback']

Description: Specifies the name of a callback function which will be called during an AJAX call. It can return HTML, a renderable array, or an array of AJAX Commands. This callback function is given the $form and $form_state parameters, allowing it to produce a result, which it returns for rendering.

Note: #ajax['callback'] and #ajax['path'] are mutually exclusive. 'callback' is easier to use and requires less code setup, but may not provide the capabilities required for some functions. When you can, use 'callback'.

Values: String containing a function name.

Usage example (poll.module):

#ajax['effect']

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

#ajax['event']

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

Values: String. Possible values: Any valid jQuery event, including 'mousedown' (for submit, imagebutton, and button), 'blur' (for textfield and textarea), 'change' (for select). Note that #ajax['event'] does not need to be explicitly specified. Although it can be manually set, usually the default value will be sufficient.

#ajax['keypress']

Description: If set to TRUE, then the element's #ajax['event'] will be triggered if the ENTER key is pressed while the element has focus.

#ajax['method']

Description: Modify the behavior of the returned HTML from an AJAX request when inserting into the #ajax['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'.

#ajax['path']

Description: This is the Drupal menu path for a callback function which will generate HTML and return the string of HTML to Drupal. The result will replace the div specified in #ajax['wrapper']. This property is infrequently used in Drupal 7 and higher, because it is set automatically if using the #ajax['callback'] property. When using #ajax['callback'] the path is automatically set to system/ajax, which provides a menu callback that can be used for many situations.

Note: 'path' and 'callback' are mutually exclusive.

Values: String containing a Drupal menu path.

#ajax['prevent']

Description: A JavaScript event to prevent when 'event' is triggered. Defaults to 'click' for #ajax on #type 'submit', 'button', and 'image_button'. Multiple events may be specified separated by spaces. For example, when binding #ajax behaviors to form buttons, pressing the ENTER key within a textfield triggers the 'click' event of the form's first submit button. Triggering Ajax in this situation leads to problems, like breaking autocomplete textfields. Because of that, Ajax behaviors are bound to the 'mousedown' event on form buttons by default. However, binding to 'mousedown' rather than 'click' means that it is possible to trigger a click by pressing the mouse, holding the mouse button down until the Ajax request is complete and the button is re-enabled, and then releasing the mouse button. For this case, 'prevent' can be set to 'click', so an additional event handler is bound to prevent such a click from triggering a non-Ajax form submission. This also prevents a textfield's ENTER press triggering a button's non-Ajax form submission behavior.

Values: String. Possible values: One or more jQuery events, with multiple events separated by space characters.

#ajax['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:

• #ajax['progress']['type'] String. Possible values: 'throbber' (default), 'bar'.
• #ajax['progress']['message'] String. An optional message to the user; should be wrapped with t().
• #ajax['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 'bar'.
• #ajax['progress']['interval'] String. The interval to be used in updating the progress bar (as defined in progress.js). Ony used if 'url' is defined and 'type' is 'bar'.

Usage example (file.module):

#ajax['trigger_as']

Description: For a non-submit, non-button element, allows selection of the submit element which will be activated when the element is triggered. For example, if a select element is ajax-enabled, and it changes, an element identified by #ajax['trigger_as']['name'] or #ajax['trigger_as']['value'] will be used as the triggering element, especially for button-level validation.

Values: Array.

Possible values

• array('name' => some_submit_or_button_name)
• array('value' => some_submit_or_button_value)

Note that if #tree == TRUE, #name encodes the parents of the element in it, as when used with form_set_error(), i.e. "level1][level2][element".

#ajax['wrapper']

Description: This property defines the HTML id attribute of an element on the page which will be replaced by the html returned by the #ajax['path'] or #ajax['callback'] function. Usually, a div element is used as the wrapper, as it provides the most flexibility for placement of elements before, after, or inside of its HTML tags. This property is required for using AJAX requests in on a form element.  Note that the entire element with this ID is replaced, not just the contents of the element.

Values: String containg a valid id attribute of an HTML element on the same page. This must not contain the '#' character that a selector would have.

Usage example (upload.module):

#array_parents

Used by: All form elements

Description: (read-only, and mostly internal). The array of names of the element's parents (including itself) in the form. This will always match the structure of $form. It is different from #parents in that #parents lists only the structure used in $form_state['values'], which is flat unless #tree is set to TRUE. Please see the complete comparison between #parents and #array_parents.

#attached

Used by: All form elements

Description: Allows loading of CSS, Javascript, libraries, or custom types when the form is built.

Values: A keyed array of type => value pairs, where the type (most often 'css', 'js', and 'library') determines the loading technique, and the value provides the options presented to the loader function. See the example below and the loader functions drupal_add_css(), drupal_add_js(), drupal_add_library(), etc.

See drupal_process_attached() for additional information.

Usage example (AJAX Example):

The above javascript #attach could also be written as:

and inline javascript can be loaded with the javascript as the key of the array, as described in drupal_add_js().

Adding settings

You add a javascript setting by using the 'data' key (as php keys can't be arrays):

Usage example (contact.pages.inc):

#attributes

Used by: actions, button, checkbox, checkboxes, container, date, fieldset, file, form, image_button, password, radio, radios, select, submit, tableselect, textarea, text_format, 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):

Note: If you are altering an existing form via hook_form_alter() or a similar means, be careful with this property! You will probably want to add to the existing array rather than writing over it, so don't follow this usage example exactly.

#autocomplete_path

Used by: textfield

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

Usage example (node.module):

#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.

#button_type

Used by: button, image_button, submit

Description: Adds a CSS class to the button, in the form form-[button_type_value]. Note that this does NOT set the HTML attribute type of the button.

Values: String

Usage example: (system.module):

#children

Used by: All elements.

Description: Internal. The rendered child elements of an element. Automatically assigned by drupal_render(), unless already set. In rare cases, you may use #children to override the output of rendered child elements, for example in a #theme_wrappers or #post_render callback. Normally, you should not have to use #children, use regular child elements instead. (See actions for an example.)

Values: String representing the rendered child elements of an element.

Usage example theme_container()):
Example in a #theme_wrappers callback.

#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):

#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):

#cols

Used by: text_format, textarea

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

Values: A positive number

Usage example (aggregator.module):

#default_tab

Used by: vertical_tabs

Description: The default open tab.

Values: String containing the HTML ID of the fieldset element for the default tab. The default value is an empty string, which results in the first tab having the focus. The fieldset's HTML ID typically takes the form of "edit-ARRAY_KEY".

Usage example:

#default_value

Used by: checkbox, checkboxes, date, hidden, radio, radios, select, tableselect, textarea, text_format, textfield, token, 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):

#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):

#description

Used by: checkbox, checkboxes, date, fieldset, file, item, password, password_confirm, radio, radios, select, text_format, 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):

#disabled

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

Description: Disables (greys out) a form input element. Setting #disabled to TRUE results in user input being ignored, regardless of how the element is themed or whether JavaScript is used to change the control's attributes.

Values: TRUE or FALSE

Usage example (system.module):

#element_validate

Used by: Any element.

Description: A list of custom validation functions. The validation functions must use form_error() or form_set_error() to flag the element as having 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 $element, $form_state, and $form as parameters, and has the form:

Usage example (file.field.inc):

Note: If you are altering an existing form element via hook_form_alter() or a similar means, be careful with this property! You will probably want to add to the existing array rather than writing over it, so in that case don't follow this usage example exactly.

You'll notice that the validation function below includes only the first two arguments. $form is the same as $form_state['complete form'], so the third parameter is in fact contained in the second parameter.

#empty

Used by: tableselect

Description: Text to display if the #options property is empty.

Values: Text, enclosed in the t() translation function.

#empty_option

Used by: select

Description: The label to show for the initial option denoting no selection in a select element. By default, the label is automatically set to "- Select -" for a required field and "- None -" for an optional field.

Values: Text, enclosed in the t() translation function.

Note: Use of this property plays a part in several possible states for a select field:

• If #required is TRUE and there is no #default_value, an empty option is added to the select control to force the user to make an active choice.
• If #empty_value or #empty_option is set and #required is FALSE (default), an empty option is added to the select control, allowing the user to choose nothing.
• If none of #required, #empty_value, #empty_option, and #default_value are set, then no empty option is added to the select control. This leaves the control in a slightly illogical state, since all user agents automatically preselect the first available option.There's no way for the user to select nothing, and the user is also not forced to make an active decision.

#empty_value

Used by: select

Description: The value for the initial option denoting no selection in a select element, which is used to determine whether the user submitted a value or not.

Values: Defaults to empty string. Can be anything except NULL.

Note: Use of this property plays a part in several possible states for a select field:

• If #required is TRUE and there is no #default_value, an empty option is added to the select control to force the user to make an active choice.
• If #empty_value or #empty_option is set and #required is FALSE (default), an empty option is added to the select control, allowing the user to choose nothing.
• If none of #required, #empty_value, #empty_option, and #default_value are set, then no empty option is added to the select control. This leaves the control in a slightly illogical state, since all user agents automatically preselect the first available option. There's no way for the user to select nothing, and the user is also not forced to make an active decision.

#error

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

#executes_submit_callback

Used by: button, image_button, submit

Description: Indicates whether or not the submit handler should be run when the form is submitted using this button element.

Values: TRUE or FALSE

#field_prefix

Used by: checkbox, machine_name, password, password_confirm, radio, select, textarea, 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):

#field_suffix

Used by: checkbox, machine_name, password, password_confirm, radio, select, textarea, 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):

#group

Used by: fieldset

Description: Specifies a group that can be used to group fieldsets into vertical tabs.

Values: A string where the value is used for the id of a form element with the #type of vertical_tabs.

Usage example (user.admin.inc):

#header

Used by: tableselect

Description: Column headers.

Values: Associative array where the keys are the field names to use for each column, and the values are the translated text to display for each column header.

#id

Description: Internal. Used to populate form elements' id property. In rare cases, you can set this value yourself on a form element, to override the default setting.

Value: HTML id string.

#input

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

#js_select

Used by: tableselect

Description: Whether to include a select all checkbox.

Values: TRUE to add a select all box to each row of the table, FALSE to omit the select all box. Only applies if #multiple is also TRUE.

#limit_validation_errors

Used by: button, image_button, submit

Description: Provides an array of sections which are parts of $form_state['values'] which should be validated, implying that sections which are not listed should not be validated. This is normally used in multistep forms in the case of a "back" button, for example, where '#limit_validation_errors' => array() would mean not to validate anything as form values on the current page are to be discarded anyway. #limit_validation_errors does not have any effect if #submit is not set. More discussion is in the form_set_error() documentation.

Values: array indicating sections of the $form_state['values'] which should be validated.

#markup

Used by: item, markup

Description: Used to set HTML that will be output on the form.

Values: Text (valid HTML)

Usage example (contact.module):

#maxlength

Used by: password, textfield

Description: The maximum amount of characters to accept as input.

Values: A positive number.

Usage example (forum.module):

#method

Used by: form

Description: The HTTP method with which the form will be submitted.

Values: get or post. Default is post.

Usage example (node.module):

#multiple

Used by: select, tableselect

Description: Indicates whether the user may select more than one item.

Values: TRUE or FALSE

Usage example (taxonomy.module):

#name

Used by: button, submit, file

Description: The name attribute of the corresponding HTML element. This can be used in element types such as submit, button and file to override the default setting.

Values: String.

#options

Used by: checkboxes, radios, select, tableselect

Description: Selectable options for a form element that allows multiple choices.

Values: An array in the form of array(t('Display value 1'), t('Display value 2')) or array('return_value1' => t('Display Value 1'), 'return_value2' => t('Display Value 2')) if specific return values are required. If returned values are identical to displayed values, you can use drupal_map_assoc() as in the example below. The #options property needs special handling for checkboxes, and works completely differently for tableselect. See the respective element descriptions for details.

Usage example (form_example_states.inc):

#parents

Used by: All

Description: Identifies parent form elements. See #tree and #parents in the handbook and the complete comparison between #parents and #array_parents.

Values: An array of element names.

Usage example (comment.module):

#post_render

Used by: All elements and forms

Description: Function(s) to call after rendering in drupal_render() has occured. The named function is called with two arguments, the rendered element and its children. It returns the (potentially) altered) element content.

Values: An array of function names to call.

Usage example:

Note: If you are altering an existing form via hook_form_alter() or a similar means, be careful with this property! You will probably want to add to the existing array rather than writing over it, so don't follow this usage example exactly.

#prefix

Used by: All elements and forms.

Description: Text or markup to include before the form element. Also see #suffix.

Values: Mixed

Usage example (poll.module):

#pre_render

Used by: All elements and forms.

Description: Function(s) to call before rendering in drupal_render() has occured. The function(s) provided in #pre_render receive the element as an argument and must return the altered element.

Values: An array of function names to call.

Usage example (filter.module):

Note: If you are altering an existing form via hook_form_alter() or a similar means, be careful with this property! As demonstrated here, you will probably want to add to the existing array rather than writing over it.

#printed

INTERNAL. Used to determine whether or not a form element has been printed yet.

#process

Used by: All

Description: An array of functions that are called when an element is processed. Using this callback, modules can "register" further actions. For example, the "radios" form type is expanded to multiple radio buttons using a processing function.

Values: Array of function names (strings)

Usage example (system.module) in system_element_info():

Note: If you are altering an existing form via hook_form_alter() or a similar means, be careful with this property! You will probably want to add to the existing array rather than writing over it, so don't follow this usage example exactly.

In this example, the function form_process_radios is called; the entire radios element is passed in as the argument. This function expands a radios element into individual radio buttons.