PHP Contact Form with Google reCaptcha V3 Example Code

Last Updated on July 27, 2023 by Subhash Jain

There are two main components/parts of Google reCaptcha Script Integration into your website form. Part I involves integration of the code into your website form page – we call it as Client Side Integration. Part II involves integration of the code into your website action page – we call it as Server Side Integration. If you want to know – How to Get Google reCaptcha Site and Secret key, please click the link.

Part I: Google reCaptcha Client Side Integration

Step 1: Paste this snippet with recaptcha Public key before the closing </head> tag on your HTML template:

<script src = 'https://www.google.com/recaptcha/api.js?render=reCaptcha_PUBLIC_KEY'> </script>
    //Paste this snippet in the JavaScript callback for an action on your website.
    <script>
    grecaptcha.ready(function(){
    grecaptcha.execute('reCaptcha_PUBLIC_KEY',
        {action: 'contact_us_action_form'}).then(function(token)
        {
            // Verify the token on the server.
            document.getElementById('captcha_token').value = token;
        });
    });
    </script>

Step 2: Insert this token in the “Hidden Field” of your form. Please note that on form load, this hidden field will populate the token value from above JS function automatically.

    <input type="hidden" id="captcha_token" name="captcha_token" />

Part II: Google reCaptcha Server Side Integration

Step 1: In the PHP action code, you need to paste at top this snippet. Please don’t forget to replace reCaptcha_PRIVATE_KEY with your registered private key.

if(isset($_POST['captcha_token'])) {
    // reCAPTCHA Settings
    $captcha = $_POST['captcha_token'];
    $ip = $_SERVER['REMOTE_ADDR'];
    $key = 'reCaptcha_PRIVATE_KEY';
    $url = 'https://www.google.com/recaptcha/api/siteverify';
    //echo $full_url;

    // reCAPTCH response
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, "$url");
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, "secret=$key&response=$captcha");
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        $output = curl_exec($ch);
        curl_close($ch);
        //echo $output;
        // If you echo above $output, you will get JSON data as similar to shown below:-
        // Json:{ "success": true, "challenge_ts": "2020-11-22T10:53:46Z", "hostname": "www.mydomain.com",
        //   "score": 0.9, "action": "contact_us_action_form" }
    $data = json_decode($output);
    //print_r($data);
    // If request was NOT a valid reCAPTCHA token for your site, terminate script execution.
    if(isset($data->success) &&  $data->success === false) {
        die('reCaptcha Invalid');
        exit;
    }
    }