Detailed explanation of php setting session (expiration, invalidation, validity period)_php skills

There are many aspects of setting up sessions in php, including setting values ​​for sessions or directly setting expiration, expiration and validity periods. The following editor will introduce to you how to use them.

Let’s first take a look at how to set the session in php.ini. Open php.ini and look for the following item in the Session settings section. The code is as follows:

session.save_path = "N;/path" 
session.save_path = "C:/Temp"　　#此处以你自己设定的路径为准

This setting allows us to perform multi-level hashing on the session storage directory, where "N" represents the directory level to be set, and the following "/path" represents the root directory path where the session file is stored. For example, we set In the following format, the code is as follows:

session.save_path = "2;C:/Temp"

The above settings mean that we store PHP session files in two-level directories. Each level of directory is 0-9 and a-z, with a total of 36 alphanumeric names as directory names. In this way, the directory where sessions can be stored can reach 36*36 , a total of 1332 folders, which I believe is enough for a single server. If your system architecture is designed to share session data with multiple servers, you can increase the directory level to 3 or more.

Session expiration time setting

Continuing with the Session topic in PHP, in PHP the life cycle of the Session is mainly set by setting session.gc_maxlifetime, such as the following code:

<&#63;php 
ini_set('session.gc_maxlifetime', 3600); //设置时间 
ini_get('session.gc_maxlifetime');//得到ini中设定值 
&#63;> 

The following is a function packaged by others, but I have not tested it. It is for reference only. The code is as follows:

<&#63;php 
function start_session($expire = 0) 
{ 
 if ($expire == 0) { 
 $expire = ini_get('session.gc_maxlifetime'); 
 } else { 
 ini_set('session.gc_maxlifetime', $expire); 
 } 
 if (emptyempty($_COOKIE['PHPSESSID'])) { 
 session_set_cookie_params($expire); 
 session_start(); 
 } else { 
 session_start(); 
 setcookie('PHPSESSID', session_id(), time() + $expire); 
 } 
} 
&#63;> 

Usage:

Add start_session(600); //Expires after 600 seconds.

How session never expires

Open the php.ini settings file and modify the three lines as follows:

1. session.use_cookies

Set the value of this to 1 and use cookies to pass sessionid

2. session.cookie_lifetime

This represents the time the SessionID is stored in the client cookie. The default is 0, which means that the SessionID will be invalidated as soon as the browser closes... It is because of this that PHP sessions cannot be used permanently! So let's set it to a number we think is big, how about 999999999, that's ok! that's all.

3. session.gc_maxlifetime

This is the time that the Session data is stored on the server side. If this time is exceeded, the Session data will be automatically deleted! So let's also set it to 99999999.

That's it, everything is ok. Of course, if you don't believe it, just test it and see - set up a session and come back after 10 days and a half. If your computer does not have a power outage or crash, you are still You can see this sessionid.

Of course, it is also possible that you do not have the authority to control the server and are not as lucky as me to be able to modify the php.ini settings. There is a way to rely on ourselves. Of course, we must use the client to store cookies, and get the sessionID Store it in the client's cookie, set the value of this cookie, and then pass this value to the session_id() function. The specific method is as follows:

<&#63;php 
session_start(); // 启动Session 
$_SESSION['count']; // 注册Session变量Count 
isset($PHPSESSID)&#63;session_id($PHPSESSID):$PHPSESSID = session_id(); 
// 如果设置了$PHPSESSID，就将SessionID赋值为$PHPSESSID，否则生成SessionID 
$_SESSION['count']++; // 变量count加1 
setcookie('PHPSESSID', $PHPSESSID, time()+3156000); // 储存SessionID到Cookie中 
echo $count; // 显示Session变量count的值 
&#63;> 

The above is the specific method of setting up a session in PHP, which involves setting the session value or directly setting the expiration, invalidation and validity period. I hope it will be helpful to everyone's learning.