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Change reCAPTCHA v2 to v3

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Home » PHP » Change reCAPTCHA v2 to v3

By: Varadharaj V

Category: PHP

Converting from Google reCAPTCHA v2 to v3 involves several steps, both on the Google reCAPTCHA side and within your PHP website. Here’s a detailed guide on how to handle the conversion, including the necessary code changes and procedures.

Overview of reCAPTCHA v2 and v3

  • reCAPTCHA v2: Requires user interaction (clicking a checkbox or solving a challenge).
  • reCAPTCHA v3: Provides a score based on user behavior without any user interaction, allowing for more seamless user experience.

Steps for Conversion

1. Register Your Site for reCAPTCHA v3

  1. Visit the Google reCAPTCHA Admin Console
  • Log in with your Google account.
  • Click on the “+” button to add a new site.
  1. Fill Out the Registration Form
  • Label: Enter a name for your site.
  • reCAPTCHA Type: Select “reCAPTCHA v3”.
  • Domains: Add your domain(s) where you want to use reCAPTCHA v3.
  • Owners: Add any additional emails for site ownership.
  • Accept the reCAPTCHA Terms of Service.
  1. Submit the Form
  • After submission, you will receive a Site Key and Secret Key. Keep these safe as you will need them for the implementation.

2. Implement reCAPTCHA v3 in Your PHP Website

Frontend: Adding reCAPTCHA v3 to Your Website

Add the following script tag in the <head> section of your HTML:

<script src="https://www.google.com/recaptcha/api.js?render=YOUR_SITE_KEY"></script>

Replace YOUR_SITE_KEY with the site key you received from Google.

Triggering reCAPTCHA v3

You will need to call grecaptcha.execute to get the token that will be sent to your server. You can do this when a form is submitted.

<form id="myForm" action="submit.php" method="POST">
  <!-- Your form fields here -->
  <input type="hidden" id="g-recaptcha-response" name="g-recaptcha-response">
  <button type="submit">Submit</button>
</form>

<script>
  grecaptcha.ready(function() {
    document.getElementById('myForm').addEventListener('submit', function(event) {
      event.preventDefault(); // Prevent form submission until token is retrieved
      grecaptcha.execute('YOUR_SITE_KEY', {action: 'submit'}).then(function(token) {
        // Add your logic to submit to your backend server here.
        document.getElementById('g-recaptcha-response').value = token;
        document.getElementById('myForm').submit();
      });
    });
  });
</script>

Explanation:

  • The action parameter in grecaptcha.execute is used to define the context of the action (e.g., submit). This can be used later for analysis and threshold settings.
  • The token generated by grecaptcha.execute is automatically placed in a hidden input field named g-recaptcha-response.
Backend: Verifying reCAPTCHA v3 in PHP

In your PHP file (submit.php), you need to verify the token with Google’s reCAPTCHA server.

<?php

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $secretKey = 'YOUR_SECRET_KEY'; // Replace with your secret key
    $response = $_POST['g-recaptcha-response'];
    $remoteIp = $_SERVER['REMOTE_ADDR'];

    // Verify the reCAPTCHA response with Google
    $url = 'https://www.google.com/recaptcha/api/siteverify';
    $data = [
        'secret' => $secretKey,
        'response' => $response,
        'remoteip' => $remoteIp
    ];

    $options = [
        'http' => [
            'header'  => "Content-type: application/x-www-form-urlencoded\r\n",
            'method'  => 'POST',
            'content' => http_build_query($data)
        ]
    ];

    $context  = stream_context_create($options);
    $result = file_get_contents($url, false, $context);
    $resultJson = json_decode($result);

    // Check the score and determine if the user is a bot
    if ($resultJson->success && $resultJson->score >= 0.5) {
        // Successful verification, proceed with the form processing
        echo "reCAPTCHA verification successful!";
    } else {
        // Verification failed
        echo "reCAPTCHA verification failed. Please try again.";
    }
}
?>

Explanation:

  • Secret Key: Replace YOUR_SECRET_KEY with the secret key you received from Google.
  • $remoteIp: The IP address of the user is sent for logging and scoring purposes.
  • Score Threshold: You can set a threshold (e.g., 0.5) to determine if the user is human. Scores range from 0.0 (likely a bot) to 1.0 (likely a human).

3. Setting Up Thresholds and Actions in the Admin Console

  1. Navigate to Your Site in the reCAPTCHA Admin Console.
  2. Set a Score Threshold:
  • Determine the score threshold that you want to use as a cutoff for human vs. bot. Google recommends starting with a 0.5 threshold.
  1. Review Action Metrics:
  • Monitor the actions you’ve set up and adjust thresholds based on user interaction data.

4. Testing and Monitoring

  • Test Your Implementation: Make sure to test with different user behaviors to validate the effectiveness of the scoring.
  • Monitor Scores and Adjust: Keep an eye on the scores from real users and adjust your thresholds accordingly in the Admin Console.
  • Error Handling: Implement error handling to manage cases where reCAPTCHA verification fails or returns a low score.

Full Example Code

HTML (Frontend):

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>reCAPTCHA v3 Example</title>
    <script src="https://www.google.com/recaptcha/api.js?render=YOUR_SITE_KEY"></script>
</head>
<body>
    <form id="myForm" action="submit.php" method="POST">
        <input type="text" name="name" placeholder="Your Name" required>
        <input type="email" name="email" placeholder="Your Email" required>
        <input type="hidden" id="g-recaptcha-response" name="g-recaptcha-response">
        <button type="submit">Submit</button>
    </form>

    <script>
        grecaptcha.ready(function() {
            document.getElementById('myForm').addEventListener('submit', function(event) {
                event.preventDefault();
                grecaptcha.execute('YOUR_SITE_KEY', {action: 'submit'}).then(function(token) {
                    document.getElementById('g-recaptcha-response').value = token;
                    document.getElementById('myForm').submit();
                });
            });
        });
    </script>
</body>
</html>

PHP (Backend):

<?php

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $secretKey = 'YOUR_SECRET_KEY';
    $response = $_POST['g-recaptcha-response'];
    $remoteIp = $_SERVER['REMOTE_ADDR'];

    $url = 'https://www.google.com/recaptcha/api/siteverify';
    $data = [
        'secret' => $secretKey,
        'response' => $response,
        'remoteip' => $remoteIp
    ];

    $options = [
        'http' => [
            'header'  => "Content-type: application/x-www-form-urlencoded\r\n",
            'method'  => 'POST',
            'content' => http_build_query($data)
        ]
    ];

    $context  = stream_context_create($options);
    $result = file_get_contents($url, false, $context);
    $resultJson = json_decode($result);

    if ($resultJson->success && $resultJson->score >= 0.5) {
        // Successful verification
        echo "reCAPTCHA verification successful!";
    } else {
        // Verification failed
        echo "reCAPTCHA verification failed. Please try again.";
    }
}
?>

Additional Tips

  1. Analyze User Behavior: Use the reCAPTCHA admin console to track and analyze user scores to refine your threshold and understand your user base better.
  2. Logging and Debugging: Implement logging of scores and responses for debugging and monitoring purposes. This helps in tuning the score thresholds over time.
  3. Fallback Mechanism: Consider implementing a fallback mechanism if the reCAPTCHA verification fails or encounters an error. This could involve displaying a more interactive challenge (like reCAPTCHA v2) to further verify genuine users.

By following these steps, you can effectively migrate from reCAPTCHA v2 to v3 in your PHP application, providing a smoother user experience while maintaining security against automated bots.

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About Varadharaj V

The founder of Kvcodes, Varadharaj V is an ERP Analyst and a Web developer specializing in WordPress(WP), WP Theme development, WP Plugin development, Frontaccounting(FA), Sales, Purchases, Inventory, Ledgers, Payroll & HRM, CRM, FA Core Customization, PHP and Data Analyst. Database Management Advance Level

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