Google recaptcha v3 - PHP

check.php

<?php

        if(isset($_POST['g-recaptcha-response']) && !empty($_POST['g-recaptcha-response'])){
            $secret_key = 'SECERET_KEY';
            $verify_captcha = file_get_contents('https://www.google.com/recaptcha/api/siteverify?secret='.$secret_key.'&response='.$_POST['g-recaptcha-response']);
            $verify_response = json_decode($verify_captcha);
            
            if($verify_response->success){
                //success
            }else{
                // check the captcha checkbox
            }
        }else{
            // empty captcha
        }

form.html

<form method="post" action="check.php">
  <script src="https://www.google.com/recaptcha/api.js" async defer></script>
  <div class="g-recaptcha" data-sitekey="SITE_KEY"></div>
  <input type="submit" value="Submit">
</form>