What is the difference between Session and Cookie in PHP?

#What is the difference between Session and Cookie in PHP?

1. Cookie data is stored in the client's browser, and Session data is stored in the server;

2. Session exists according to the browser process, and the cookie's survival time can be set And adjustments;

3. Session must use Cookie.

PHP Session Variable

When you operate an application on your computer, you open it and do something Change and then close it. It's a lot like a conversation. The computer knows who you are. It knows when you open and close apps. However, on the Internet a problem arises: since HTTP addresses cannot maintain state, the web server has no idea who you are and what you do.

PHP session solves this problem by storing user information on the server for subsequent use (such as user name, purchased items, etc.). However, session information is temporary and will be deleted after the user leaves the site. If you need to store information permanently, you can store the data in a database.

The working mechanism of Session is to create a unique id (UID) for each visitor and store variables based on this UID. The UID is stored in a cookie or passed through the URL.

Usage examples

<?php//  表单提交后...$posts = $_POST;//  清除一些空白符号foreach ($posts as $key => $value) {
    $posts[$key] = trim($value);}$password = md5($posts["password"]);$username = $posts["username"]; $query = "SELECT `username` FROM `user` WHERE `password` = &#39;$password&#39; AND `username` = &#39;$username&#39;";//  取得查询结果$userInfo = $DB->getRow($query); if (!empty($userInfo)) {
    //  当验证通过后，启动 Seindex.html> 验证 session里的`admin`是否为 `true`<?php//  防止全局变量造成安全隐患$admin = false;//  启动会话，这步必不可少session_start();//  判断是否登陆if (isset($_SESSION["admin"]) && $_SESSION["admin"] === true) {
    echo "您已经成功登陆";} else {
    //  验证失败，将 $_SESSION["admin"] 置为 false
    $_SESSION["admin"] = false;
    die("您无权访问");}?>

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