Drupal 7 Module Development

Submit callback
The submit callback is a little more interesting but not by much:
Chapter 6
function artwork_form_submit($form, &$form_state) {
global $user;
$artwork = &$form_state['artwork'];
// Set the artwork's uid if it's being created at this time.
if (empty($artwork->uid)) {
$artwork->uid = $user->uid;
}
$artwork->title = $form_state['values']['title'];
$artwork->revision = $form_state['values']['revision'];
// Notify field widgets.
field_attach_submit('artwork', $artwork, $form, $form_state);
// Save the artwork.
artwork_save($artwork);
// Notify the user.
drupal_set_message(t('Artwork saved.'));
}
$form_state['redirect'] = 'artwork/' . $artwork->aid;
First we pull the old artwork object out of the $form_state variable. Next we set
its user, if it's a new artwork, and populate it with the few values we have from the
form. We've already confirmed that those values are valid in the validation hook.
field_attach_submit(), much like its sibling functions, lets the Field system
respond to the fact that a form was just submitted and do whatever it wants to
do. Then we simply save the artwork.
It is important to note here that the submit callback is doing extremely little. It's just
glue code between the form and the artwork_save() function, really. That's a good
thing. It means that artwork operations, such as saving, are not dependent on the
form system.
Never do serious processing in a form submit callback. The
actual work of saving an entity and its data should happen in the
entity's save routines. The form submit callback is just glue code.
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