WordPress Custom Hook For User Registration Validation

// Hook into the user registration process to validate user input
add_action('user_register', 'custom_user_registration_validation');

function custom_user_registration_validation($user_id) {
    // Get the user object
    $user = get_userdata($user_id);

    // Check if the user's email domain is allowed
    $allowed_domains = array('example.com', 'anotherdomain.com');
    $user_email_domain = substr($user->user_email, strpos($user->user_email, '@') + 1);
    if (!in_array($user_email_domain, $allowed_domains)) {
        // If the domain is not allowed, delete the user and notify the administrator
        wp_delete_user($user_id);
        wp_mail('admin@example.com', 'Disallowed Email Domain', 'A user tried to register with a disallowed email domain: ' . $user_email_domain);
        return;
    }

    // Assign a custom role to the user
    $user->set_role('custom_role');

    // Log the registration for auditing purposes
    $log_message = 'User ' . $user->user_login . ' registered with email ' . $user->user_email;
    error_log($log_message);
}

// Also validate user input on the registration form submission
add_filter('registration_errors', 'custom_registration_form_validation', 10, 3);

function custom_registration_form_validation($errors, $sanitized_user_login, $user_email) {
    // Check for any existing users with the same email address
    if (email_exists($user_email)) {
        $errors->add('email_exists', 'An account with this email address already exists.');
    }

    return $errors;
}