Stop Spam On Your Website By Implementing Google reCAPTCHA PHP Script

A friend of mine complained to me about him getting lots of spam messages and replies in his forum website. He said not only are they annoying, but contain adult and porn links. I decided to implement a simple captcha to help fight spam using google reCAPTCHA.
If you are in same problem, follow the steps below to code and implement a captcha to help fight spam in your website.

1. Head over to google reCAPTCHA page
2. Sign up by submitting your website URL
3. You will be given a public and private key
4. Downlnad the google reCAPTCHA here
5. Extract the recaptchalib.php and upload to the root folder of your site
6. Next to do is implementing the captcha in your site as outline below:-
   • Add the below code to your html <form>

     
     require_once('recaptchalib.php');
        $publickey = "your_public_key_here";  // you got this from signup page
       echo recaptcha_get_html($publickey);
     

     Example

     <form method="post" action="verify.php">
         <?php
          require_once('recaptchalib.php');
        $publickey = "your_public_key_here";  // you got this from signup page
       echo recaptcha_get_html($publickey);
       ?>
       <input type="submit" />
      </form>
     

     Don’t forget to set $publickey by replacing your_public_key_here with your API public key.

   • Next, we need to add the below code in our html form file (verify.php).

     
     <?php
       require_once('recaptchalib.php');
       $privatekey = "your_private_key_here";
       $resp = recaptcha_check_answer ($privatekey,
         $_SERVER["REMOTE_ADDR"],
         $_POST["recaptcha_challenge_field"],
         $_POST["recaptcha_response_field"]);
     
     if (!$resp->is_valid) {
      // What happens when the CAPTCHA was entered incorrectly
      die ("The reCAPTCHA wasn't entered correctly. Go back and try it again." . "(reCAPTCHA said: " . $resp->error . ")");
      } else {
        //Your code here to handle a successful verification
     }
     ?>
     

     Also make sure your form is set to get the form variables using $_POST, instead of $_REQUEST, and that the form itself is using the POST method.

If you have done the steps above successfully, congratulation! You won’t be haunted again by spam.
If you encounter difficulties implementing this or have any contribution to make, i will be glad to hear your comments.