问如何验证谷歌Recaptcha V3响应？

EN

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

<form id="contactForm" method="post" action="contact">
    <!-- other form inputs -->
    <input type="hidden" id="gRecaptchaResponse" name="gRecaptchaResponse">
    <input type="submit" name="contact_submit" value="Send message">
</form>

<script>
    contactForm.addEventListener('submit', event => {
        event.preventDefault()
        validate(contactForm)
    });
</script>

function validate(form) {
    //perform optional error checking on form. If no errors then request a token and put it into the hidden field
    getRecaptchaToken(form)
}

//some other (optional) form validation functions

function getRecaptchaToken(form) {
    grecaptcha.ready(function() {
        grecaptcha.execute($reCAPTCHA_site_key, {action: 'contactForm'}).then(function(token) {
            gRecaptchaResponse.value = token //set the value of the hidden field
            form.submit() //submit the form
        });
    });
}

//get the IP address of the origin of the submission
$ip = $_SERVER['REMOTE_ADDR'];

//construct the url to send your private Secret Key, token and (optionally) IP address of the form submitter to Google to get a spam rating for the submission (I've saved '$reCAPTCHA_secret_key' in config.php)
$url =  'https://www.google.com/recaptcha/api/siteverify?secret=' . urlencode($reCAPTCHA_secret_key) . '&response=' . urlencode($g_recaptcha_response) . '&remoteip=' . urlencode($ip);

//save the response, e.g. print_r($response) prints { "success": true, "challenge_ts": "2019-07-24T11:19:07Z", "hostname": "your-website-domain.co.uk", "score": 0.9, "action": "contactForm" }
$response = file_get_contents($url);

//decode the response, e.g. print_r($responseKeys) prints Array ( [success] => 1 [challenge_ts] => 2019-07-24T11:19:07Z [hostname] => your-website-domain.co.uk [score] => 0.9 [action] => contactForm )
$responseKeys = json_decode($response, true);

//check if the test was done OK, if the action name is correct and if the score is above your chosen threshold (again, I've saved '$g_recaptcha_allowable_score' in config.php)
if ($responseKeys["success"] && $responseKeys["action"] == 'contactForm') {
    if ($responseKeys["score"] >= $g_recaptcha_allowable_score) {
        //send email with contact form submission data to site owner/ submit to database/ etc
        //redirect to confirmation page or whatever you need to do
    } elseif ($responseKeys["score"] < $g_recaptcha_allowable_score) {
        //failed spam test. Offer the visitor the option to try again or use an alternative method of contact.
    }
} elseif($responseKeys["error-codes"]) { //optional
    //handle errors. See notes below for possible error codes
    //personally I'm probably going to handle errors in much the same way by sending myself a the error code for debugging and offering the visitor the option to try again or use an alternative method of contact
} else {
    //unkown screw up. Again, offer the visitor the option to try again or use an alternative method of contact.
}

   {
     "success": true|false,      // whether this request was a valid reCAPTCHA token for your site
     "score": number             // the score for this request (0.0 - 1.0)
     "action": string            // the action name for this request (important to verify)
     "challenge_ts": timestamp,  // timestamp of the challenge load (ISO format yyyy-MM-dd'T'HH:mm:ssZZ)
     "hostname": string,         // the hostname of the site where the reCAPTCHA was solved
     "error-codes": [...]        // optional
   }

<?php  //contact.php

    require_once('config.php');

    //do server-side validation of other form fields

    if (/*form has been submitted and has passed server-side validation of the other form fields*/) {
        $ip = $_SERVER['REMOTE_ADDR'];
        $url =  'https://www.google.com/recaptcha/api/siteverify?secret=' . urlencode($reCAPTCHA_secret_key) . '&response=' . urlencode($g_recaptcha_response) . '&remoteip=' . urlencode($ip);
        $response = file_get_contents($url);
        $responseKeys = json_decode($response, true);

        if ($responseKeys["success"] && $responseKeys["action"] == 'contactForm') {
            if ($responseKeys["score"] >= $g_recaptcha_allowable_score) {
                //send email with contact form submission data to site owner/ submit to database/ etc
                //redirect to confirmation page or whatever you need to do
            } elseif ($responseKeys["score"] < $g_recaptcha_allowable_score) {
                //failed spam test. Offer the visitor the option to try again or use an alternative method of contact.
            }
        } elseif($responseKeys["error-codes"]) { //optional
            //handle errors. See notes below for possible error codes
            //(I handle errors by sending myself an email with the error code for debugging and offering the visitor the option to try again or use an alternative method of contact)
        } else {
            //unkown screw up. Again, offer the visitor the option to try again or use an alternative method of contact.
        }

        exit;

    } else { //(re)display the page with the form

        echo <<<_END

            <!DOCTYPE html>
            <html lang="en">
                <head>
                    <title>Contact | Your website</title>
                    <link rel="stylesheet" href="css/style.css">
                    <script src="https://www.google.com/recaptcha/api.js?render=$reCAPTCHA_site_key"></script>
                </head>
                <body>

                    <!-- header etc -->

                    <form id="contactForm" method="post" action="contact">
                        //other form inputs
                        <input type="hidden" id="gRecaptchaResponse" name="gRecaptchaResponse">
                        <input type="submit" name="contact_submit" value="Send message">
                    </form>
                    <script>
                        contactForm.addEventListener('submit', event => {
                            event.preventDefault()
                            validate(contactForm)
                        });
                    </script>

                    <!-- footer etc -->

                    <script>
                        function validate(form) {
                            //perform optional client-side error checking of the form. If no errors are found then request a token and put it into the hidden field. Finally submit the form.
                            getRecaptchaToken(form)
                        }

                        //some (optional) form field validation functions

                        function getRecaptchaToken(form) {
                            grecaptcha.ready(function() {
                                grecaptcha.execute($reCAPTCHA_site_key, {action: 'contactForm'}).then(function(token) {
                                    gRecaptchaResponse.value = token
                                    form.submit()
                                });
                            });
                        }
                    </script>
                </body>
            </html>

_END;

<?php //config.php

//other site settings

// Google reCAPTCHA v3 keys
// For reducing spam contact form submissions

// Site key (public)
$reCAPTCHA_site_key = 'N0t-a-real-0N3_JHbnbUJ-BLAHBLAH_Blahblah';

// Secret key
$reCAPTCHA_secret_key = 'N0t-a-real-0N3_i77tyYGH7Ty6UfG-blah';

// Min score returned from reCAPTCHA to allow form submission
$g_recaptcha_allowable_score = 0.5; //Number between 0 and 1. You choose this. Setting a number closer to 0 will let through more spam, closer to 1 and you may start to block valid submissions.

<html>
    <head>
        <script src='https://www.google.com/recaptcha/api.js?render=6Le7-FkUAAAAADDSsTVBvpoUB5MkesNKgPVemFf-UD'></script>
    </head>
    <body> 
    <script>
    // when form is submit
    $('form').submit(function() { 
        // we stoped it
        event.preventDefault();
        // needs for recaptacha ready
        grecaptcha.ready(function() {
            // do request for recaptcha token
            // response is promise with passed token
            grecaptcha.execute('6Le7-FkUAAAAADDSsTVBvpoUB5MkesNKgPVemFf-UD', {action: 'create_comment'}).then(function(token) {
                // add token to form
                $('form').prepend('<input type="hidden" name="token" value="' + token + '">');
                $('form').prepend('<input type="hidden" name="action" value="create_comment">');
                // submit form now
                $('form').unbind('submit').submit();
            });;
        });
    });

    </script>

    <form action="verify.php" method="post">
        <input type="text" name="name" placeholder="Your name" required >
        <input type="email" name="email" placeholder="Your email address" required>
        <textarea name="message" placeholder="Type your message here...." required></textarea>   

        <input type="submit" name="submit" value="SUBMIT">

    </form>

    </body>

</html>

$token = $_POST['token'];
$secret = 'ur secret';
$action = $_POST['action'];
// now you need do a POST requst to google recaptcha server.
// url: https://www.google.com/recaptcha/api/siteverify.
// with data secret:$secret and response:$token 

<script>
  grecaptcha.ready(function() {
   grecaptcha.execute('YOUR_SITE_KEY', {action: 'MyForm'})
   .then(function(token) {
    console.log(token)
    document.getElementById('g-recaptcha-response').value =    token;
   }); 
  }); 
 </script> 

<form action="verify.php" method="post">
  <input type="hidden" id="g-recaptcha-response" name="g-recaptcha-response">
  <input type="text" name="name" placeholder="Your name" required >
  <input type="email" name="email" placeholder="Your email address" required>
  <input type="submit" name="submit" value="SUBMIT" >
</form>