Understanding and application of cache-related knowledge in PHP Session-PHP Tutorial-php.cn

Understanding and application of cache-related knowledge in PHP Session

jacklove

Release： 2023-03-25 13:48:01

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PHP Session plays an important role in phpcaching. This article provides a detailed explanation of its related knowledge.

PHP Session Variables

When you work with an application on your computer, you open it, make changes, 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.

Start PHP Session

Before you can store user information in a PHP session, you must first start the session.

Note: session_start() Functionmust be located before the tag:

<?php session_start(); ?><html><body></body></html>

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The above code will register the user's session with the server , so that you can start saving user information and a UID is assigned to the user session.

Storing Session Variables

The correct way to store and retrieve session variables is to use PHP $_SESSION Variable:

<?php
session_start();// 存储 session 数据$_SESSION[&#39;views&#39;]=1;?><html><head><meta charset="utf-8"><title>菜鸟教程(runoob.com)</title></head><body><?php// 检索 session 数据echo "浏览量：". $_SESSION[&#39;views&#39;];?></body></html>

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Output:

In the following example, we create a simple page-view counter. The isset() function detects whether the "views" variable has been set. If the "views" variable is set, we increment the counter. If "views" does not exist, create the "views" variable and set it to 1:

<?php
session_start();if(isset($_SESSION[&#39;views&#39;])){    $_SESSION[&#39;views&#39;]=$_SESSION[&#39;views&#39;]+1;}else{    $_SESSION[&#39;views&#39;]=1;}echo "浏览量：". $_SESSION[&#39;views&#39;];?>

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Destroy Session

If you want to delete some session data, you can use unset() Or the session_destroy() function.

unset() function is used to release the specified session variable:

<?php
session_start();if(isset($_SESSION[&#39;views&#39;])){    unset($_SESSION[&#39;views&#39;]);}?>

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You can also completely destroy the session by calling the session_destroy() function:

<?phpsession_destroy();?>

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This article discusses PHP Session The content and usage methods are introduced. For more learning materials, please pay attention to the php Chinese website to view.

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