Add ReCaptcha to comments Wordpress

add_recaptcha.php

<?php
// Add to functions.php

add_action( 'wp_enqueue_scripts', 'add_recaptcha_js', 5, 1 );
function add_recaptcha_js() {
// Registration reCAPTHCA api.js, version - null, in footer - false
    wp_register_script( 'recaptcha', 'https://www.google.com/recaptcha/api.js?hl=en', array(), null, false );
// Include reCAPTHCA api.js
    wp_enqueue_script( 'recaptcha' );
}

add_filter('comment_form_submit_button', 'filter_comment_form_submit_button', 10, 2);

function filter_comment_form_submit_button($submit_button) {
    /* ReCaptcha only for anonymous users 
    global $user_ID;
    if (!$user_ID){
        $recaptcha_site_key = 'Site Key';
        echo '<div class="g-recaptcha" data-sitekey="'.$recaptcha_site_key.'"></div>';
    }
    */
    /* For all users */
    $recaptcha_site_key = 'Site key';
    echo '<div class="g-recaptcha" data-sitekey="'.$recaptcha_site_key.'"></div>';

    $submit_before = '<div class="form-group">';
    $submit_after = '</div>';
    return $submit_before . $submit_button . $submit_after;
}

function verify_recaptcha_response() {
    $recaptcha_secret_key = 'Secret Key';
    $recaptcha_site_key = 'Site Key';
    if ( isset ( $_POST['g-recaptcha-response'] ) ) {
        $captcha_response = $_POST['g-recaptcha-response'];
    } else {
        return false;
    }

// Verify the captcha response from Google
    $response = wp_remote_post(
        'https://www.google.com/recaptcha/api/siteverify',
        array(
            'body' => array(
                'secret' => $recaptcha_secret_key,
                'response' => $captcha_response
            )
        )
    );
    $success = false;
    if ( $response && is_array( $response ) ) {
        $decoded_response = json_decode( $response['body'] );
        $success = $decoded_response->success;
    }
    return $success;
}

add_action('preprocess_comment', "preprocess_comment_cb");
function preprocess_comment_cb($commentdata) {
    /* ReCaptcha only for anonymous users
    global $user_ID;
    if ($user_ID) {
        return $commentdata;
    }
    */
    if ( ! verify_recaptcha_response() ) {
        echo '<p style="font-size: 1rem;">You are not verified reCaptcha test. Return to the <a href="#" onclick="history.go(-1);">previous page </a> and try again.';
        exit;
    }
    return $commentdata;
}