<?php
class NewsletterSignUpWidget extends Widget{
   static $title = "";
   static $cmsTitle = "Newsletter Sign Up";
   static $description = "Newsletter Sign Up - requires page with URL segement 'thanks-for-joining' in the CMS";
}

class NewsletterSignUpWidget_Controller extends Widget_Controller {
   function NewsletterSignUpForm() {
      $fields = new FieldSet(
         new TextField("FirstName", "Enter your first name: ", ""),
         new EmailField("Email", "Enter your email address: ", "")
      );

      $actions = new FieldSet(
         new FormAction("doform", "Subscribe")
      );

      $required =new RequiredFields(
         "FirstName",
         "Email"
      );

      return new Form($this, "dosignupform", $fields, $actions, $required);
   }

   function dosignupform($data) {
      $member = new Member();
      $member->FirstName = $data['FirstName'];
      $member->Email = $data['Email'];
      $member->write();

      if($group = DataObject::get_one('Group', "Code = 'Newsletter'")){
         $member->Groups()->add($group);
      }

      // Redirect to a page thanking people for registering, this needs creating int he CMS
      Director::redirect('/thanks-for-joining');
   }
}

$NewsletterSignUpForm