A Drupal fieldset example (Drupal form group)

Drupal form fieldset FAQ: How do I build a Drupal form using one or more fieldset areas to group my form elements into logical components (like 'shipping address', 'billing address', 'credit card information', and so on)?

As inferred by the question, you group Drupal form elements using the Drupal fieldset element. You define a fieldset, then add form elements to that fieldset using a simple sub-array syntax. For example, in the following Drupal source code example I define a fieldset using an array like this: