PHP如何创建多个会话？

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

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

Answer 2

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>";