First, we need an API key, so head on over to https://www.google.com/recaptcha/admin. To gain access to this page you’ll need to be logged into a Google account. You’ll be asked to register your website, so give it a suitable name, then list domains (for example tutsplus.com) where this particular reCAPTCHA will be used. Subdomains (such as webdesign.tutsplus.com and code.tutsplus.com) are automatically taken into account.
With that done you’ll be given a site key and its partner secret key:
Site key you will add in html page:
Secret key you will add in php_helper/_contact-process.php file: