How to deal with Cookie and Session invalidation issues in PHP language development?

With the development of the Internet, website applications are increasingly using Cookies and Sessions to save user login status, shopping cart information and other data. However, due to network instability, browser settings and other reasons, Cookies and Sessions often encounter problems with failure. This article will introduce how to deal with Cookie and Session invalidation issues in PHP language development.

1. Cookie invalidation problem

Cookie is a small data file stored on the web browser side, which can transfer data between multiple pages. Generally speaking, there are two ways for cookies to expire, namely expiration and deletion by the user.

In PHP, setting the cookie expiration time parameter can control the cookie expiration time. For example, the following sample code sets a cookie named "username" with an expiration time of 1 hour:

// 设置Cookie过期时间为1小时
setcookie('username', 'Tom', time() + 3600);

When the cookie expires, the browser will automatically delete this cookie. At this time, the $_COOKIE array will no longer contain this cookie information.

In addition, users can manually delete cookies through browser settings. In this case, it will also cause the $_COOKIE array to no longer contain the cookie information.

In order to avoid the impact of Cookie expiration, we should first determine whether the Cookie exists and whether it has expired before using it. For example, the following sample code determines whether the "username" Cookie exists, and if it exists, outputs the value of the Cookie:

if(isset($_COOKIE['username'])){
    echo '欢迎你，'.$_COOKIE['username'];
}else{
    echo '请先登录';
}

2. Session Invalidation Problem

Session is a kind of behavior in the Web A server-side data storage mechanism used to save the user's session state. When a user visits the website, the server assigns a unique Session ID to each user and stores the Session ID in a cookie and passes it to the browser. When the browser sends a request again, it will bring this cookie, and the server determines the user's session status based on the Session ID.

Different from Cookie, there are two main ways for Session to expire, namely server-side Session expiration and browser-side closing causing Session ID to become invalid.

You can control the expiration time of Session through ini settings, such as:

// 设置Session过期时间为1小时
ini_set("session.gc_maxlifetime", 3600);
session_start();

When Session expires, you can destroy the current user's Session through functions such as unset($_SESSION) or session_destroy(). data.

However, closing the browser or the user closing the browser tab will cause the Session ID to become invalid. In order to solve this problem, we can use the following methods:

(1) Use the method of regularly refreshing the page to maintain the status of the Session.

(2) Use js to send ajax requests regularly and maintain the status of the Session.

For example,
JS code:

// 定时发送ajax请求
setInterval(function(){
    $.get("keepSessionAlive.php");
}, 300000); // 每隔5分钟发送一次请求

PHP code (keepSessionAlive.php):

<?php
session_start();

It will be automatically triggered when the user does not perform any operations for a period of time Requests are sent regularly to maintain the validity of the Session ID.

3. Summary

When using Cookies and Sessions, you need to pay attention to handling invalidation issues to avoid unnecessary impact on the application. You can maintain the status of Cookie and Session by setting expiration time and sending requests regularly. At the same time, the appropriate solution needs to be selected based on the needs and specific circumstances of the application.

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