Creating dropdown dependant forms

custom_form.info

; $Id$
name = Custom Form dependant dropdown
description = Dropdown dependant form
project = Dependant dropdown
core = 6.x
version = 6.x-1.0

custom_form.module

<?php

/**
 * Reference: http://xebee.xebia.in/2011/06/14/drupal-webform-add-a-dynamic-select-option-list/
 * The following piece of code is based on the blog post above written by Anubhav
 */


/**
 * Implement hook_menu().
 *
 * Note that each item has both an entry point to prepare the form, and also
 * a callback function that provides and AHAH menu callback.
 */
function custom_form_menu() {
  $items = array();

// Automatically generate textfields.
$items['form/aha-form-test'] = array(
  'title' => 'Degrading dependent dropdown',
  'page callback' => 'drupal_get_form',
  'page arguments' => array('custom_form_dropdown'),
  'access callback' => TRUE,
  'weight' => 4,
  'type' => MENU_LOCAL_TASK,
//   'file' => 'ahah_example_dependent_dropdown.inc',
);

$items['form/aha-form-test/callback'] = array(
  'page callback' => 'custom_form_dropdown_callback',
  'access callback' => TRUE,
//   'file' => 'ahah_example_dependent_dropdown.inc',
  'type' => MENU_CALLBACK,
);


return $items;
}


/**
 * Form builder function to create a form showing dependent dropdowns. The
 * second dropdown has its values populated based on the first.
 * @param $form_state
 * @param $my_values
 */
function custom_form_dropdown(&$form_state, $my_values = array()) {

  $form = array();

  // get the list of options to populate the first dropdown
  $initial_options = _custom_form_get_first_dropdown_options();

  // get the list of options to populate the first dropdown
//   $initial_options = _ahah_example_get_first_dropdown_options();

  $form['explanation'] = array(
    '#type' => 'markup',
    '#value' => '<div>' . t('This is an example of a properly degrading dynamic form. It will work correctly with or without
       AJAX enabled. However, it has to provide an extra hidden button to change the values in the dependent dropdown.') . '</div>',
  );


  // if we have a value for the first dropdown from $form_state['values'] we use
  // this both as the default value for the first dropdown and also as a
  // parameter to pass to the function that retrieves the options for the
  // second dropdown.
  $master_selection = !empty($form_state['values']['master_dropdown']) ? $form_state['values']['master_dropdown'] : t('ASDA');

  // Here is where the magic happens.
  $form['master_dropdown'] = array(
    '#type' => 'select',
    '#title' => 'Master Dropdown',
    '#options' => $initial_options,
    '#default_value' => $master_selection,
    '#ahah' => array(
//       'path' => 'examples/ahah_example/dependent_dropdown/callback',
      'path' => 'form/aha-form-test/callback',

      'wrapper' => 'dependent-dropdown-wrapper',
      // 'event' => 'change', // default value: does not need to be set explicitly.
    ),
    '#attributes' => array('class' => 'master-dropdown'),
  );


  $form['dependent_dropdown_holder'] = array(
    '#tree' => TRUE,
    '#prefix' => '<div id="dependent-dropdown-wrapper">',
    '#suffix' => '</div>',
  );

  $form['dependent_dropdown_holder']['dependent_dropdown'] = array(
    '#type' => 'select',
    '#title' => t('Dependent Dropdown (changes based on master dropdown)'),

    // when the form is rebuilt during processing (either AJAX or multistep),
    // the $master_selction variable will now have the new value and so the
    // options will change.
    '#options' => _custom_form_get_second_dropdown_options($master_selection),
    '#default_value' => isset($my_values['dependent_dropdown']) ? $my_values['dependent_dropdown'] : '',
  );


  return $form;
}


/**
 * Helper function to populate the second dropdown. This would normally be
 * pulling data from the database.
 *
 * @param key. This will determine which set of options is returned.
 *
 * @return array of options
 */
function _custom_form_get_second_dropdown_options($key = '') {  //
  $options = array(
    t('shop1') => _custom_form_get_shops('shop1'),
    t('shop2') => _custom_form_get_shops('shop2'),
    t('shop3') => _custom_form_get_shops('shop3'),
    t('shop4') => _custom_form_get_shops('shop4'),

  );
  if (isset($options[$key])) {
    return $options[$key];
  }
  else {
    return array();
  }

//   return $options;
}

/**
 *  Change this query to adapt to your needs
 */
function _custom_form_get_shops($key = '') {

  // Query to search for ...
  $sql = "SELECT * FROM %s";

  $result = db_query($sql, $key);

  // WE STORE THEM (FULL NODE) IN AN ARRAY
  while( $row = db_fetch_array( $result ) ) {
    $options[] = $row['name'];

  }

  return $options;

}


/**
 * Helper function to populate the first dropdown. This would normally be
 * pulling data from the database.
 *
 * @return array of options
 */
function _custom_form_get_first_dropdown_options() {
  // drupal_map_assoc() just makes an array('Strings' => 'Strings'...).
  return drupal_map_assoc(array(t('shop1'), t('shop2'), t('shop3'), t('shop4')));
}

/**
 * The AHAH callback. It processes the form using ahah_example_callback_helper()
 * and then
 */
function custom_form_dropdown_callback() {
  $form = ahah_custom_form_custom_webforms_callback_helper();

  $changed_elements = $form['dependent_dropdown_holder'];

  // Prevent duplicate wrappers.
  unset($changed_elements['#prefix'], $changed_elements['#suffix']);

  $output = theme('status_messages') . drupal_render($changed_elements);

  drupal_json(array(
  'status'   => TRUE,
  'data'     => $output,
  ));
}



/**
 * Does the very standard things that must be done in any normal callback.
 * Used by each callback in this example module.
 */
function ahah_custom_form_callback_helper() {

  $form_state = array('storage' => NULL, 'submitted' => FALSE);
  $form_build_id = $_POST['form_build_id'];
  $form = form_get_cache($form_build_id, $form_state);
  $args = $form['#parameters'];
  $form_id = array_shift($args);
  $form_state['post'] = $form['#post'] = $_POST;

  // Enable the submit/validate handlers to determine whether AHAH-submittted.
  $form_state['ahah_submission'] = TRUE;
  $form['#programmed'] = $form['#redirect'] = FALSE;
  drupal_process_form($form_id, $form, $form_state);
  $form = drupal_rebuild_form($form_id, $form_state, $args, $form_build_id);
  return $form;
}

can anyone knows how to create a dependent dropdown list in php ajax for mutiple tables.