html-forms-validation-example.php

<?php

/**
 * Validate HTML Forms.
 *
 * @param  string           $error
 * @param  \HTML_Forms\Form $form
 * @param  array            $data
 * @return string
 */
add_filter('hf_validate_form', function ($error, $form, $data) {
    if ($form->slug !== 'contact-us') {
        return $error;
    }

    if (empty($data['first_name']) || empty($data['last_name'])) {
        return 'required_field_missing';
    }

    if (empty($data['email'] || ! is_email($data['email']))) {
        return 'invalid_email';
    }

    if (empty($data['terms'])) {
        return 'invalid_terms';
    }

    $recaptcha = new \ReCaptcha\ReCaptcha(
        env('RECAPTCHA_PRIVATE_KEY')
    );

    $response = $recaptcha->setExpectedHostname(
        wp_parse_url(home_url(), PHP_URL_HOST)
    )->verify(
        $data['g-recaptcha-response'] ?? '',
        $_SERVER['REMOTE_ADDR']
    );

    if (! $response->isSuccess()) {
        return 'invalid_captcha';
    }

    return $error;
}, 10, 3);

/**
 * Customize the HTML Forms invalid captcha error.
 *
 * @return string
 */
add_filter('hf_form_message_invalid_captcha', function () {
    return __('Invalid recaptcha response.', 'html-forms');
});

/**
 * Customize the HTML Forms invalid terms error.
 *
 * @return string
 */
add_filter('hf_form_message_invalid_terms', function () {
    return __('You must agree to the terms of service.', 'html-forms');
});