How to use PHP functions to implement single sign-on and cross-domain authentication for user login and logout?

With the development of websites and applications, user login and logout are one of the essential functions. In some cases, we may need to implement single sign-on and cross-domain authentication functions to improve user experience and security. This article describes how to use PHP functions to achieve these two functions and provides corresponding code examples.

1. Single Sign-On

Single Sign-On (SSO) means that users only need to log in once to use the same set of credentials for identity verification in multiple applications. A mechanism for authentication. Implementing single sign-on can avoid the tedious process of logging in to every application and provide a convenient user experience.

The following is a simple single sign-on sample code:

<?php
session_start();

// 检查用户是否已经登录
function check_login() {
    if (isset($_SESSION['user_id'])) {
        return true;
    }
    return false;
}

// 用户登录
function login($user_id) {
    $_SESSION['user_id'] = $user_id;
}

// 用户注销
function logout() {
    unset($_SESSION['user_id']);
}

// 使用示例
if (!check_login()) {
    // 用户未登录，跳转到登录页面
    header("Location: login.php");
    exit;
}

// 用户已登录，继续处理其他逻辑
// ...
?>

In the above example, we created a check_login() function to check whether the user has Log in. If the user is not logged in, jump to the login page; if the user is logged in, continue processing other logic.

During the login process, we can call the login($user_id) function to save the user's login status in $_SESSION. During the logout process, the logout() function can be called to clear the user's login status.

By calling the above function in each application to realize the single sign-on function, the user only needs to log in once to obtain the sharing of login status in other applications.

2. Cross-domain authentication

In some cases, we may need to share user login status between different domain names (or sub-domain names) to achieve cross-domain authentication. The following is a simple cross-domain authentication sample code:

<?php
session_start();

// 检查用户是否已经登录
function check_login() {
    if (isset($_SESSION['user_id'])) {
        return true;
    }
    return false;
}

// 校验 Token 是否有效
function validate_token($token) {
    // 根据具体需求进行校验
    if ($token === 'valid_token') {
        return true;
    }
    return false;
}

// 使用示例
if (isset($_GET['token'])) {
    $token = $_GET['token'];
    if (validate_token($token)) {
        // Token 有效，将用户标识存入 Session
        $_SESSION['user_id'] = 'user123';
    }
}

if (!check_login()) {
    // 用户未登录或 Token 无效，跳转到登录页面
    header("Location: login.php");
    exit;
}

// 用户已登录，继续处理其他逻辑
// ...
?>

In the above example, we added a validate_token($token) function to verify whether the provided Token is valid. According to actual needs, verification can be performed based on the information in the Token, such as decrypting the Token or querying the database for verification.

In the process of cross-domain authentication, we can pass the Token through URL parameters, and then use the validate_token($token) function in the target page to verify and verify the user's login The state is saved in $_SESSION.

Call the above function in each application to implement the cross-domain authentication function, and the user's login status can be shared between different domain names (or sub-domain names).

In actual applications, we can adjust the above code according to needs and specific business logic, and combine database query, encryption and decryption and other operations to implement more complex user login, logout and authentication functions.

Summary:

This article introduces how to use PHP functions to implement single sign-on and cross-domain authentication functions for user login and logout. Single sign-on can provide a convenient user experience and avoid the tediousness of logging in in every application; while cross-domain authentication can share the user's login status between different domain names (or sub-domain names) to achieve unified identity authentication. mechanism. By rationally using PHP functions, we can flexibly implement these two functions and expand and customize them according to actual needs. I hope this article can be helpful to readers.

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