Drupal 7 Module Development

Building an Admin Interface
Form submission process
When an HTML form built with Form API is submitted, Drupal looks for two
specifically named functions—a validate function and a submit function. These
functions are named by taking the form ID and appending either _validate()
or _submit() depending on which function you are writing.
The validate function does additional validation beyond what Drupal provides. For
instance if you wanted to check to see if a zip code is valid. Even if validation fails
on one element, all validation functions are still called, so Drupal can return multiple
errors in a single form. However, if any validation function fails, execution never
proceeds to the submit function.
Validate functions are optional. If you don't need any additional
validation, then you don't have to write one. In this case, Drupal
will just do its default validation. For more information on how to
write validate functions, see the Form API documentation at the links
referenced earlier in the chapter.
Once the form passes validation, the submit function is called. This is where the real
work is done—saving settings, sending e-mail, and creating content among other
things. The form submit function is one of the main workhorses of Drupal modules.
As a module writer you will spend an inordinate amount of time writing submit
functions and support code for submit functions. This is good, because it means you
are spending time on the code that is unique to your project, and not recreating the
wheel every time you want to turn a field red because a required field is missing.
So let's apply this to the User Warn configuration form. The form ID for our
configuration form is user_warn_form, so our submit function will be named
user_warn_form_submit().
Form submit functions take two arguments. $form is the original Form API array
for the submitted form, and $form_state is an associative array containing
information specific to this submission. In particular, $form_state['values']
contains all the submitted form values keyed on their name properties. In general,
$form_state['values'] is the only thing you will need to worry about in validate
and submit functions.
/**
* Save configuration settings for User Warn module.
*/
function user_warn_form_submit($form, &$form_state) {
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