Form API Reference : Drupal

Drupal uses and API to build forms so in order to build them it's necessary to use an array in conjunction with a reference.

so for example in ticket #3326, this is the form which I need to edit (I've added the span tag and aria labels)

$form['submit'] = [ '#type' => 'submit', '#value' => t('Subscribe'), '#prefix' => '', '#suffix' => '' ]; $form['#submit'] = ['corp_newsletter_form_submit']; } return $form; }