如何为WordPress插件添加用户注册功能

<form method="post" action="">
    <input type="text" name="username" placeholder="用户名" />
    <input type="email" name="email" placeholder="电子邮件" />
    <input type="password" name="password" placeholder="密码" />
    <input type="password" name="confirm_password" placeholder="确认密码" />
    <input type="submit" name="submit" value="注册" />
</form>

function register_user() {
    if (isset($_POST['submit'])) {
        $username = sanitize_user($_POST['username']);
        $email = sanitize_email($_POST['email']);
        $password = $_POST['password'];
        $confirm_password = $_POST['confirm_password'];
        
        // 检查用户名和电子邮件是否已经存在
        if (username_exists($username) || email_exists($email)) {
            $error_message = '用户名或电子邮件已经存在。';
        } elseif ($password !== $confirm_password) {
            $error_message = '密码和确认密码不匹配。';
        } else {
            // 创建新用户
            $user_id = wp_create_user($username, $password, $email);
            
            // 设置新用户为已激活状态
            wp_update_user(array('ID' => $user_id, 'role' => 'subscriber'));
            
            // 可选：发送欢迎邮件给新用户
            wp_new_user_notification($user_id, $password);
            
            // 注册成功后的跳转页面
            wp_redirect(home_url('/注册成功/'));
            exit;
        }
    }
}
add_action('init', 'register_user');

function login_form() {
    if (!is_user_logged_in()) {
        $login_args = array(
            'redirect' => home_url('/'),
            'form_id' => 'loginform',
            'label_username' => __('用户名'),
            'label_password' => __('密码'),
            'label_remember' => __('记住我'),
            'label_log_in' => __('登录'),
            'remember' => true
        );
        wp_login_form($login_args);
    } else {
        wp_loginout(home_url('/'), true);
    }
}
add_shortcode('login_form', 'login_form');