PHP How can I create multiple sessions?

Question

I want to be able to switch back and forth between sessions in php. Here is my current code:

<?php

session_name("session1");
session_start();
$_SESSION["name"] = "1";
echo "<pre>", print_r($_SESSION, 1), "</pre>";
session_write_close();

session_name("session2");
session_start();
$_SESSION["name"] = "2";
echo "<pre>", print_r($_SESSION, 1), "</pre>";
session_write_close();

session_name("session1");
session_start();
echo "<pre>", print_r($_SESSION, 1), "</pre>";

I want it to output

Array
(
    [name] => 1
)
Array
(
    [name] => 2
)
Array
(
    [name] => 1
)

but it is outputting

Array
(
    [name] => 1
)
Array
(
    [name] => 2
)
Array
(
    [name] => 2
)

Is it possible to switch between sessions like that? I don't need two sessions running at the same time, but I do need to be able to switch between them. When I run this code, I get two cookies: session1 and session2 with the same value.

Thanks for any help!

Answer 1

As the comments to the existing answer indicate, the offered solution might not be ideal and I would like to provide some alternative. Let it be a function named sane_session_name(), which looks like this:

function sane_session_name($name)
{
    session_name($name);
    if(!isset($_COOKIE[$name]))
    {
        $_COOKIE[$name] = session_create_id();
    }
    session_id($_COOKIE[$name]);
}

By using the "sane" subsitution for session_name() in the OP's original code, we get this:

<?php
sane_session_name("session1");
session_start();
$_SESSION["name"] = "1";
echo "<pre>", print_r($_SESSION, 1), "</pre>";
session_write_close();

sane_session_name("session2");
session_start();
$_SESSION["name"] = "2";
echo "<pre>", print_r($_SESSION, 1), "</pre>";
session_write_close();

sane_session_name("session1");
session_start();
echo "<pre>", print_r($_SESSION, 1), "</pre>";

and it will yield the desired output:

Array
(
    [name] => 1
)

Array
(
    [name] => 2
)

Array
(
    [name] => 1
)

What is different?

To point out the difference between this answer and the raidenace's answer:

• In raidenace's answer two sessions are created for all clients shared among all visitor of the website.
• With this answer two sessions are created for each visitor to the website. Consequently this would allow that in the $_SESSION superglobal different content can be stored for visitor Alice and Bob, while in the other two website visitor Alice an Bob would "share the data", and rather pointlessly a cookie named PHPSESSID with the value session2 is set each time and send back and forth.

Security

To protect those "multiple (per user) sessions" from session fixation and session hijacking, we can further use this litte function

function sane_session_start($name)
{
    ini_set("session.use_strict_mode",true);
    ini_set("session.cookie_httponly",true);
    session_name($name);
    if(!isset($_COOKIE[$name]))
    {
        $_COOKIE[$name] = session_create_id();
    }
    session_id($_COOKIE[$name]);
    session_start();
    session_regenerate_id(true);
    $_COOKIE[$name] = session_id();
}

and have the OP's code look like this:

<?php
sane_session_start("session1");
$_SESSION["name"] = "1";
echo "<pre>", print_r($_SESSION, 1), "</pre>";
session_write_close();

sane_session_start("session2");
$_SESSION["name"] = "2";
echo "<pre>", print_r($_SESSION, 1), "</pre>";
session_write_close();

sane_session_start("session1");
echo "<pre>", print_r($_SESSION, 1), "</pre>";

Answer 2

What you need to use is session_id() instead of session_name()

<?php

session_id("session1");
session_start();
echo session_id();
$_SESSION["name"] = "1";
echo "<pre>", print_r($_SESSION, 1), "</pre>";
session_write_close();

session_id("session2");
echo session_id();
session_start();
$_SESSION["name"] = "2";
echo "<pre>", print_r($_SESSION, 1), "</pre>";
session_write_close();

session_id("session1");
echo session_id();
session_start();
echo "<pre>", print_r($_SESSION, 1), "</pre>";
session_write_close();

session_id("session2");
echo session_id();
session_start();
echo "<pre>", print_r($_SESSION, 1), "</pre>";

This will print:

session1

Array
(
    [name] => 1
)

session2

Array
(
    [name] => 2
)

session1

Array
(
    [name] => 1
)

session2

Array
(
    [name] => 2
)

session_id is an identifier for a session, which helps in distinguishing sessions. session_name is only a named alias for the current session