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recaptcha v3

Responsive image

HTML code

to render the reCAPTCHA on the front-end.

index.html

<html>
<head>
    <title>Google recapcha v3 demo</title>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js"></script>
    <script src="https://www.google.com/recaptcha/api.js?render=******YOUR-SITE-KEY******"></script>
</head>
<body>
    <h1>Google reCAPTHA Demo</h1>
    <form id="comment_form">
        <input type="email" name="email" placeholder="Type your email" size="40"><br><br>
        <textarea name="comment" rows="8" cols="39"></textarea><br><br>
        <input type="submit" name="submit" value="Post comment"><br><br>
    </form>
    <script src="script.js"></script>
    </body>
</html>  

replace ******YOUR-SITE-KEY****** with your site key.

script.js


    $('#comment_form').submit(function() {
        // we stoped it
        event.preventDefault();
        var email = $('#email').val();
        var comment = $("#comment").val();
        // wait for recaptacha ready
        grecaptcha.ready(function() {
            // do request for recaptcha token
            // response is promise with passed token
            grecaptcha.execute('******YOUR-SITE-KEY******', {action: 'create_comment'}).then(function(token) {
                // add token to form
                $('#comment_form').prepend('<input type="hidden" name="g-recaptcha-response" value="' + token + '">');
                $.post("form.php",{email: email, comment: comment, token: token}, function(result) {
                    if(result.success) {
                        alert('Thanks for posting comment.')
                    } else {
                        alert('You are spammer ! Get the @$%K out.')
                    }
                });
            });
        });
    });

replace ******YOUR-SITE-KEY****** with your site key.

server-side

On the server-side we are going to use PHP for now. So on the Form submit, we will check the POST variable.

form.php


<?php
  $email;$comment;$captcha;
  $email = filter_input(INPUT_POST, 'email', FILTER_VALIDATE_EMAIL);
  $comment = filter_input(INPUT_POST, 'comment', FILTER_SANITIZE_STRING);
  $captcha = filter_input(INPUT_POST, 'token', FILTER_SANITIZE_STRING);
  if(!$captcha){
    echo '<h2>Please check the captcha form.</h2>';
    exit;
  }
  $secretKey = "******YOUR-SECRET-KEY******";
  $ip = $_SERVER['REMOTE_ADDR'];

  // post request to server
  $url = 'https://www.google.com/recaptcha/api/siteverify';
  $data = array('secret' => $secretKey, 'response' => $captcha, 'remoteip' => $ip);

  $options = array(
    'http' => array(
      'header'  => "Content-type: application/x-www-form-urlencoded\r\n",
      'method'  => 'POST',
      'content' => http_build_query($data)
    )
  );
  $context  = stream_context_create($options);
  $response = file_get_contents($url, false, $context);
  $responseKeys = json_decode($response, true);
  header('Content-type: application/json');
  if($responseKeys["success"] && $responseKeys["action"] === "create_comment" && $responseKeys["score"] >= 0.5) {
    echo json_encode(array('success' => 'true'));
  } else {
    echo json_encode(array('success' => 'false'));
  }
?>

replace ******YOUR-SECRET-KEY****** with your secret key.

Last Updated: Oct 17, 2024