Four ways to automatically clear session in php

PHP automatically clears Session

Session is a server-side state management mechanism commonly used in web development. The Session mechanism can store information about users throughout the website hierarchy for use as they browse the website. Although Sessions provide convenience in making websites easier to use and more interactive, if Sessions are not cleaned up in time, they will occupy the server's memory. Therefore, it is very reasonable to expect expired Sessions to be deleted through automatic cleanup.

In PHP, automatic cleaning of Session can be achieved through the following methods.

1. Configuration in php.ini

In the php.ini file, you can set two options, session.gc_probability and session.gc_divisor. When gc_probability divided by gc_divisor equals 0, the Session's garbage collection mechanism will be started.

For example:

session.gc_probability = 1
session.gc_divisor = 100

This means that the Session garbage collection mechanism will be started with a 1% probability. The default value for this option is 1, which means that every user request attempts to start the garbage collection mechanism.

To automatically start the garbage collection mechanism at the same time, you can add the following option:

session.gc_maxlifetime = 1440

This means that the Session is not idle for 1440 seconds (i.e. 24 minutes) It will be deleted after access.

2. Set the expiration time when the Session is created

Use the ini_set() function to set the expiration time of the Session. For example:

ini_set('session.gc_maxlifetime', 1440);
session_set_cookie_params(1440);

In this way, the Session will expire and be deleted after 1440 seconds (i.e. 24 minutes) .

3. Using timers

Timers can clear expired Sessions at fixed intervals. You can use the setInterval() function to create a timer, and then perform Session cleanup operations in the timer.

For example:

setInterval(function() {

$expire_time = time() - 1440;
$files = glob(session_save_path() . '/sess_*');
foreach ($files as $file) {
    if (file_exists($file)) {
        if (filemtime($file) < $expire_time) {
            unlink($file);
        }
    }
}

}, 600);

Here, the timer will be executed every 10 minutes Session cleanup. The path of the Session file is obtained through the session_save_path() function. By default, it is /tmp.

When using timers, you also need to pay attention to concurrency processing, because other users may be creating new Sessions when the timer performs cleanup operations.

4. Manually clear the Session

Finally, if the above method cannot meet the needs, you can also manually clear the Session. For example, when the user exits, the Session can be destroyed through the session_destroy() function.

For example:

session_start();
//Perform user exit operation
session_destroy();

Manually cleaning the Session requires the developer to maintain it himself. More time and effort, but also provides greater granular control.

Summary

PHP automatically cleans up the Session while improving website performance, and can also prevent the Session from occupying too much server memory. By configuring php.ini, Session expiration time, timer and manual cleaning, developers can clean the Session in different scenarios to improve the stability and availability of the website.

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