Mailster, Formidable integration

add_action('frm_after_create_entry', 'mailster_formidable_subscribe', 30, 2);
add_action('frm_after_update_entry', 'mailster_formidable_subscribe', 30, 2);

function mailster_formidable_subscribe($entry_id, $form_id){
  if ( $form_id == 55 ) { //change 55 to the ID of your form

	// define to overwrite existing users
	  $overwrite = true;

	  // add with double opt in
	  $double_opt_in = false;

	  // prepare the userdata from a $_POST request. only the email is required
	  $userdata = array(
		'email' => $_POST['item_meta'][535], //change 535, 534, 533 to the ID of your email, first name and last name field
		'firstname' => $_POST['item_meta'][533],
		'lastname' => $_POST['item_meta'][534],
		'status' => $double_opt_in ? 0 : 1,
	);
	  $subscriber_id = mailster( 'subscribers' )->add( $userdata, $overwrite );

	  if ( ! is_wp_error( $subscriber_id ) ) {

		// your list ids
	  $list_ids = 1;
	  mailster( 'subscribers' )->assign_lists( $subscriber_id, $list_ids );

	} else {
		// actions if adding fails. $subscriber_id is a WP_Error object
	}
  }
}