Zend_Service_ReCaptcha provides a client for the » reCAPTCHA Web Service. Per the reCAPTCHA site, "reCAPTCHA is a free CAPTCHA service that helps to digitize books." Each reCAPTCHA requires the user to input two words, the first of which is the actual CAPTCHA, and the second of which is a word from some scanned text that Optical Character Recognition (OCR) software has been unable to identify. The assumption is that if a user correctly provides the first word, the second is likely correctly entered as well, and can be used to improve OCR software for digitizing books.

In order to use the reCAPTCHA service, you will need to » sign up for an account and register one or more domains with the service in order to generate public and private keys.

Instantiate a Zend_Service_ReCaptcha object, passing it your public and private keys:

To render the reCAPTCHA, simply call the getHTML() method:

When the form is submitted, you should receive two fields, 'recaptcha_challenge_field' and 'recaptcha_response_field'. Pass these to the reCAPTCHA object's verify() method:

Once you have the result, test against it to see if it is valid. The result is a Zend_Service_ReCaptcha_Response object, which provides an isValid() method.

It is even simpler to use the reCAPTCHA Zend_Captcha adapter, or to use that adapter as a backend for the CAPTCHA form element. In each case, the details of rendering and validating the reCAPTCHA are automated for you.

Zend_Service_ReCaptcha_MailHide can be used to hide email addresses. It will replace a part of an email address with a link that opens a popup window with a reCAPTCHA challenge. Solving the challenge will reveal the complete email address.

In order to use this component you will need » an account to generate public and private keys for the mailhide API.

The example above will display "[email protected]" where "..." has a link that opens up a popup window with a reCAPTCHA challenge.

The public key, private key, and the email address can also be specified in the constructor of the class. A fourth argument also exists that enables you to set some options for the component. The available options are listed in the following table:

Zend_Service_ReCaptcha_MailHide options

Option	Description	Expected Values	Default Value
linkTitle	The title attribute of the link	string	'Reveal this e-mail address'
linkHiddenText	The text that includes the popup link	string	'...'
popupWidth	The width of the popup window	int	500
popupHeight	The height of the popup window	int	300

The configuration options can be set by sending them as the fourth argument to the constructor or by calling setOptions($options), which takes an associative array or an instance of Zend_Config.