How does drupal choose which function to process a form submit?

Question

I'm really confused,can someone clarify this?

Answer 1

Check the entries for 'Validating Forms' and 'Submitting Forms' in the Form API Quickstart Guide - by default Drupal will look for a function that is named [form_id]_submit, but this is just the default behavior. You can override this (or add more than one submit callback) by putting the callback function names in the #submit attribute of the form declaration (see http://api.drupal.org/api/drupal/developer--topics--forms_api_reference.html/6#submit-prop).