HomePage.php

<?php

class HomePage extends Page {

}

class HomePage_Controller extends Page_Controller {
        static $allowed_actions = array('BuyForm', 'doBuy', 'complete', 'failed', 'beforeBuy');

        public function BuyForm() {
                $fields = new FieldList(
                        new FieldGroup('Customer Details',
                                TextField::create('FirstName', 'First name')->setAttribute('required', true),
                                new TextField('LastName', 'Last name'),
                                new EmailField('Email', 'e-mail Address'),
                                new PhoneNumberField('Phone')
                        ),
                        new FieldGroup('Terms & Conditions',
                                new LiteralField('TC', '<div class="typography">' . $this->getActiveDeal()->TermsAndConditions . '</div>'),
                                new CheckboxField('TCAgree', 'I accept the terms & conditions')
                        ),
                        new HiddenField('DealID', 'DealID', $this->getActiveDeal()->ID)
                );
                $actions = new FieldList(
                        new FormAction('doBuy', 'Next'),
                        new LabelField('note', 'You will be directed to a secure DPS page, then returned to this website.')
                );
                $required = new RequiredFields(array('FirstName', 'LastName', 'Email', 'Phone', 'TCAgree', 'DealID'));
                $form = new Form($this, __FUNCTION__, $fields, $actions, $required);
                $form->loadDataFrom($this->request->postVars());
                return $form;
        }

        public function doBuy($data, $form) {
                var_dump($form->validate());
                die('called');
        }