I am assuming you have site key and secret in place. Follow this step.
In your HTML file, add the script.
<script src="https://www.google.com/recaptcha/api.js?render=put your site key here"></script>
Also, do use jQuery for easy event handling.
Here is the simple form.
<form id="comment_form" action="form.php" method="post" >
<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>
You need to initialize the Google recaptcha and listen for the ready event. Here is how to do that.
<script>
// when form is submit
$('#comment_form').submit(function() {
// we stoped it
event.preventDefault();
var email = $('#email').val();
var comment = $("#comment").val();
// needs for recaptacha ready
grecaptcha.ready(function() {
// do request for recaptcha token
// response is promise with passed token
grecaptcha.execute('put your site key here', {action: 'create_comment'}).then(function(token) {
// add token to form
$('#comment_form').prepend('<input type="hidden" name="g-recaptcha-response" value="' + token + '">');
$.post("form.php",{email: email, comment: comment, token: token}, function(result) {
console.log(result);
if(result.success) {
alert('Thanks for posting comment.')
} else {
alert('You are spammer ! Get the @$%K out.')
}
});
});
});
});
</script>
Here is the sample PHP file. You can use Servlet or Node or any backend language in place of it.
<?php
$email;$comment;$captcha;
if(isset($_POST['email'])){
$email=$_POST['email'];
}if(isset($_POST['comment'])){
$comment=$_POST['comment'];
}if(isset($_POST['token'])){
$captcha=$_POST['token'];
}
if(!$captcha){
echo '<h2>Please check the the captcha form.</h2>';
exit;
}
$secretKey = "put your secret key here";
$ip = $_SERVER['REMOTE_ADDR'];
// post request to server
$url = 'https://www.google.com/recaptcha/api/siteverify?secret=' . urlencode($secretKey) . '&response=' . urlencode($captcha);
$response = file_get_contents($url);
$responseKeys = json_decode($response,true);
header('Content-type: application/json');
if($responseKeys["success"]) {
echo json_encode(array('success' => 'true'));
} else {
echo json_encode(array('success' => 'false'));
}
?>
Here is the tutorial link: https://codeforgeek.com/2019/02/google-recaptcha-v3-tutorial/
Hope it helps.