Suppose you are using the WP-Members registration form essentially as an opt-in to your MailChimp list. Essentially, you want anyone who fills out the form to be added to the MailChimp opt-in process.
This requires you to have the MailChimp extension installed and a subscribe field set up and configured. This filter will take that field and make it a hidden field, essentially triggering the MailChimp opt-in process for all users. [Read more…]