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How to use session in php?

coldplay.xixiOriginal: 2020-07-22 14:04:433930browse

How to use session in php: 1. Start PHP Session and place the [session_start()] function in front of the [] tag; 2. Use [PHP $_SESSION] to store Session variables; 3. Use [unset() 】Destroy Session.

How to use session in php:

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PHP Session variable

When you operate an application on your computer , you open it, make some 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.

Starting a PHP Session

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

Note: session_start()The function must be located before the 100db36a723c770d327fc0aef2ce13b1 tag:

Example

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

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

Storing Session Variables

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

Example

<?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>

Output:

浏览量：1

In the following example, we create a simple page-view counter. isset()The 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:

Instance

<?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;];
?>

Destroy Session

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

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

Example

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

You can also call session_destroy() Function to completely destroy the session:

Example

<?php
session_destroy();
?>

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