silverstripe-frameworktest/code/recaptcha/RecaptchaTestPage.php

<?php
class RecaptchaTestPage extends Page {
	
}

class RecaptchaTestPage_Controller extends Page_Controller {
	
	function Form() {
		$fields = new FieldSet(
			new TextField('MyText')
		);
		if(class_exists('RecaptchaField')) {
			$fields->push(new RecaptchaField('MyRecaptcha'));
		} else {
			$fields->push(new LiteralField('<p class="message error">RecaptchaField class not found</p>'));
		}
		
		$form = new Form(
			$this,
			'Form',
			$fields,
			new FieldSet(
				new FormAction('submit', 'submit')
			),
			new RequiredFields(array('MyText'))
		);
		
		return $form;
	}
	
	function submit($data, $form) {
		$form->sessionMessage('Hooray!', 'good');
		
		return Director::redirectBack();
	}
	
}