Form API By : Payel Ghosh

Mail : g.payel@puneitlabs.com

Introducing form API Rather than output HTML, we create an array and let the engine generate

the HTML.

Since we are dealing with a representation of the form as structured data, we can add, delete, reorder and change forms.

This is handy when you want to modify a form created by a different module easily.

Any form element can be mapped to any theme function.

Additional form validation or processing can be added to any form.

Form is easy to build

drupal_get_form ($mydetail_form). Retrieves and builds mydetail_form

mydetail_form() function builds an array

mydetail_form_validate() validates the mydetail form

mydetail_form_submit() function processes

Understanding Form Processing

Form elements Textfield Textarea Password Select radios Checkboxes Value Hidden Date File Upload Fieldset Submit

Properties allowed in all elements #type #access #after_build #theme #prefix #suffix #title #weight ('#delta' => 10) #default_value

Modules modify the formhook_form_alter() • this is the primary way to change, override the form that are created by modules

other than your old one.• Any module that implements the form_alter() hook can modify anything in the

form.• Before building the form form_alter() hook is called.

Birthdays.module

function birthdays_form_alter($form_id, &$form) { if ($form_id ==

'profile_field_form') { $form['#submit'] = (array)$form['#submit'] +

array('birthdays_profile_form_submit' => array()); }}

Form modification after it’s built#after_build• #after_build is an optional array of functions to be called once the current form

element has been built.

• When the entire form has been built, a final call is made to the optional function whose names may be defined in $form [‘#after_build’].

Example:

image.module

$form['thumbnail']['#after_build'][] = 'image_form_add_thumbnail';

Finding theme function• The benefits to having our own theme function are that we’re able to parse, munge,

and add to $output as we please.

function theme_mydetail_form($form) {

$output = drupal_render($form);

return $output;}

• You can direct Drupal to use a function that does not match the formula “theme_ plus form ID name” by specifying a #theme property for a form.

$form['#theme'] = ‘mydetail_form_special_theme';

Form validationDrupal has a built-in mechanism for highlighting form elements that fail validation and displaying an error message to the user.

function mydetail_form_validate($form_id,$form_values){

if ($form_values['first_name']== 'abc') {

form_set_error ( t(' FIrstname is not valid'));}

Element specific form validationIt is possible to set validators for individual form elements To do that, set the #validate property for the element to an array with the name of the validation function as the key and any arguments you want to send along as the value.

$allowed_flavors = array(t('spicy'), t('sweet'));

$form['flavor'] = array(

'#type' => 'textfield',

'#title' => 'flavor',

'#validate' => array('formexample_flavor_validate' => array($allowed_flavors)));

function formexample_flavor_validate($element, $allowed_flavors) {

if (!in_array($element['#value'], $allowed_flavors) {

form_error($element, t('You must enter spicy or sweet.');

}}

Submit functionThe submit function is the function that takes care of actual form processing after the form has been validated.

It only executes if form validation passed completely

function mydetail_form_submit($form, $form_values) {

// Now send user to node number 3.

return 'node/3';

}

The redirection of the submit function can be overridden by defining a #redirect property in the form

Multipage formfunction mymultiform_multiform($form_values = NULL) {

$form['#multistep'] = TRUE;

$step = isset($form_values) ? (int) $form_values['step'] : 1;

$form['step'] = array(

'#type' => 'hidden',

'#value' => $step + 1

);switch ($form_state[‘step’]) {

case 1:

...

case 2:

...

case 3:

...

}

Multipage form

Step - 1 step - 2

step - 3step - 4

Thank you