Captcha is a very useful mechanism to avoid automated abuse of your sites and applications. In particular, reCAPTCHA is a Google powered service that offers a free and simple way to implement a captcha protection field in your forms or pages. Zend Framework 2 implements his own components to handle captcha and a specific one to handle reCAPTCHA service. At the moment, the ZF2 documentation is very usefull if you want to integrate a reCAPTCHA in your Zend/Form component, but lacks in describing how to use reCAPTCHA service component alone. Actually Zend/Form is very powerful, but sometimes a developer need to use standard html to implement his own forms and this prevents to use ReCaptcha as Zend/Form element.
To reach our achievement, we will implement a reCAPTCHA service that can be use all over the project to generate captchas and test them against values inserted by user. This service will be used principally in views and controllers. The following code implementation assumes that you have a working ZF2 project, configured as described in official documentation.