Where Are $_Session Variables Stored

Where are $_SESSION variables stored?

The location of the $_SESSION variable storage is determined by PHP's session.save_path configuration. Usually this is /tmp on a Linux/Unix system. Use the phpinfo() function to view your particular settings if not 100% sure by creating a file with this content in the DocumentRoot of your domain:

<?php
    phpinfo();
?>

Here is the link to the PHP documentation on this configuration setting:

http://php.net/manual/en/session.configuration.php#ini.session.save-path

How server stores session variables created using PHP?

Sessions may but don't have to use database backend. The rest of your statements are generally fine (cookies, session_id).

Default session storage in PHP is a file in /tmp folder - path can be checked by printing session.save_path.

To summarize, sessions can utilize:

1. File(s) on hard disk
2. File(s) in memory e.g. in /dev/shm and its subfolders (/tmp can also reside in RAM)
3. Database - session tables may reside on disk or in memory
4. Specialized memory backends

Response to your comment: You understand the process of sharing session data between browser and web server. But session storage used is important for you if you want to access session data manually (outside of PHP script).

If you store user_id in $_SESSION variable, then yes - you can use it to query database for user related information using it from within your PHP script in any subsequent request.

How to use store and use session variables across pages?

Reasoning from the comments to this question, it appears a lack of an adjusted session.save_path causes this misbehavior of PHP’s session handler. Just specify a directory (outside your document root directory) that exists and is both readable and writeable by PHP to fix this.

Where is $_SESSION data stored and when it gets deleted?

They are stored on the php server, and get deleted after a certain timeout when the server hasn't had a request from the associated client. The timeout is configurable in php.ini or directly from your script.

Session Variables Not Being Stored

If you want your session variables to appear on any other page, then session_start(); must be included inside all your pages using sessions.

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Footnotes:

Should you happen in the future to get the following error message: headers already sent, you could add ob_start(); just above session_start();

Relevant links:

• http://www.php.net/manual/en/features.sessions.php
• http://www.php.net/session_start
• http://www.php.net/ob_start
• http://www.php.net/header

where does session save?

The session data that you read and write using $_SESSION is stored on server side, usually in text files in a temporary directory. They can not be accessed from outside.

The thing connecting a session to a client browser is the session ID, which is usually stored in a cookie (see the comments for exceptions to that rule). This ID is, and should be, the only thing about your session that is stored on client side.

If you delete the cookie in the browser, the connection to that session is lost, even if the file on the server continues to exist for some time.

The session.save_path variable influences the location on the server where the session data is stored. If you are not the server's administrator, it is usually not necessary to change it.

Where should be data stored? Session variables OR Hidden fields?

Primarily opinion based, but each has pros and cons.

Storing in $_SESSION:

• Pro: allows you to store private data that you don't necessarily want to fire back to the user, ie: either application-internal data, or the user's private data that should not be returned into the page, such as credit card details, passwords, and other personal information.
• Con: The session will expire after its configured timeout, and the user will lose their work.

Storing in hidden fields:

• Basically reverse the pros and cons for $_SESSION.
• IMHO, using hidden fields like this is a huge kludge.

The ideal way is to use a custom session handler to store the session data in a way that it is not lost when the session expires.

Where session variable is stored in java web application

The "session" variable consists of two pieces, a very small session identifier which is stored on the client usually named jSessionId and stored as a cookie. But, the sessionId may also be encoded into URLs.

The second piece of a session is the actual data, and it is stored on the server. Possibly in a server-side database if the your server is part of a multi-server cluster. Each session is identified by that sessionId and the client sends it with every request. That is why it is designed to be very small.

How to store a variable in php using session

at the top of page

session_start();

then to set session variable

$_SESSION['id'] = $someID;

To retrieve the value of id

$pid = $_SESSION['id'];

Further more read more about session here

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