Possible Duplicate:
What is basic concept behind hooks?
How does comment_field_extra_fields() implement hook_field_extra_fields()? How is a hook implemented by another function? Does it extend another class to use a hook function?
Drupal Answers is a question and answer site for Drupal developers and administrators. It only takes a minute to sign up.
Sign up to join this community
Anybody can ask a question
Anybody can answer
The best answers are voted up and rise to the top
module_implements()andmodule_invoke()in the API, and this excellent resouce – Clive♦ Aug 24 '12 at 20:56