Drupal Form Api

this presentation explains the basics of drupal form api for drupal 5

1. Form API
By : Payel Ghosh
Mail : [email protected]

2. 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.

3. 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

4. Understanding Form Processing

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

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

7. Modules modify the form
hook_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()); }}

8. 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';

9. 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';

10. Form validation
Drupal 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'));}

11. Element specific form validation
It 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.');
}}

12. Submit function
The 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

13. Multipage form
function 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:
...
}

14. Multipage form
Step - 1
step - 2
step - 3step - 4

15. Thank you