Session

Session support consists of a way to preserve certain data across subsequent accesses to the web server.

By default, each query to a webserver is independent from the others. With session, it is possible to keep some data on the server, and retrieve them at each access.

It relies on the session_* functions, and the $_SESSION superglobal variable.

<?php

    if (isset($_SESSION['x'])) {
        print 'x was already set with the value ' . $_SESSION['x'];
    }

    $_SESSION['x'] = rand(0, 10);
    print 'Giving the value ' . $_SESSION['x'] . 'to x, in the session';

?>

Documentation

See also Session in PHP: Creating, Destroying, and Working With Session in PHP, Sessions security and Fixing PHP Session Issues: Troubleshooting and Solutions.

Related : Superglobal Variables, Object Persistence, Persistence, Session Fixation, Session Hijacking, Horizontal Scaling, Race Condition, Single Sign On (SSO), State, JSON Web Token (JWT), Load Balancer, SessionHandlerInterface, SessionIdInterface, SessionUpdateTimestampHandlerInterface, APCu, Shared Memory, Temporary, Time To Live (TTL)