I get the following erros on selecting the selectbox. Here onchang of this field will populate another checkbox with city details id zipcode using ajax callback.
$zipcode_options = get_all_zipcodes_ascending(); // Populate Ort on auktion clone. $selected = isset($auktion->zip_code) ? $auktion->zip_code : NULL; $selected = isset($form_state['values']['zip_code']) ? $form_state['values']['zip_code'] : $selected; $ort_options = _ajax_city_dropdown_options($selected); $form['zip_code'] = [ '#type' => 'select', '#title' => t('PLZ'), '#options' => $zipcode_options, '#default_value' => isset($auktion->zip_code) ? $auktion->zip_code : "", '#select2' => ['width' => '100%', 'placeholder' => t('Enter a zipcode'), 'allowClear' => TRUE], '#empty_option' => '', '#validated' => TRUE, '#required' => TRUE, '#ajax' => array( 'event' => 'change', 'callback' => 'ajax_example_dependent_dropdown_callback', 'wrapper' => 'dropdown-second-replace', ), ];
Referenced many links but cannot find a solution to resolve this issue.
References:
https://www.drupal.org/node/586576
populate drop down from results using ajax
Sponsored by SupremePR