php - Is this possible to unset one variable from other session?

Question

If I want to unset one variable in current user session then I can use command unset($_SESSION['something']).

Is this possible to unset only one variable from other session in case when I know PHPSESSID value (can I do it without changing current user session)? I would like check if session of PHPSESSID still exist, if exist then unset($_SESSION['something']) of chosen PHPSESSID.

It's possible, but it's not exactly straight forward or easy. I'd suggest that this is bad design, one user shouldn't need to do anything in another user's session. Try to look for a different way to solve whatever you want to solve. — deceze, Jan 27 '12 at 09:27
I have other solution. I can enable CRON to take over the session and change one variable. `session_id($variable_PHPSESSID); session_start();` But I would like do that in other way. I thought it can be done in more easiest way. But also I will think about reorganize my script. — Lucas, Jan 27 '12 at 09:34
The issue is that have more than one session seems a bad practice. It should be better use the effort in re-implement the whole thing, IMHO.- — Igor Parra, Jan 27 '12 at 09:38
possible duplicate of [Is it possible to clear a different session's variable?](http://stackoverflow.com/questions/5836780/is-it-possible-to-clear-a-different-sessions-variable) — Gordon, Jan 27 '12 at 09:40

score 2 · Accepted Answer · edited May 23 '17 at 12:16

Is this possible to unset only one variable from other session in case when I know PHPSESSID value

Yes this is possible and you need to know the session id of that session you would like to unset the variable/value from.

can I do it without changing current user session?

If you want to do it with standard PHP functions, it's not possible without switching the session. With third-party libraries you can do that w/o switching the session.

I would like check if session of PHPSESSID still exist, if exist then unset($_SESSION['something']) of chosen PHPSESSID.

This is pretty similar to an answer to php destroy a session which is not the current session, but only deleting a specific member:

$unsetFromSessionID = ... ; # set your session id from where you want to unset from
$unsetVariableName = 'something'; # set the variable name

$backupSessionID = session_id($unsetFromSessionID);
session_start(); # load session data
unset($_SESSION[$unsetVariableName]);
session_commit(); # save changes to disc

session_id($backupSessionID); # switch to current session
session_start();

If you want to find out if that other session was active or not, this is not possible with this method and from within PHP because PHP will create a new, empty session on session_start() in case it did not exists.

The alternative is to work with the session store directly, e.g. by looking for the session file on disc, loading it's contents, removing a variable and saving it back. A PHP library that is able to do that is Serialized, it ships with an example of a Session File Viewer which might be a good starting point.

See also: How to tell if a session is active?

score 0 · Answer 2 · answered Jan 30 '18 at 06:06

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If you want to change the session id on each log in, make sure to use session_regenerate_id(true) during the log in process.

   session_start(); 
   session_regenerate_id(true);

answered Jan 30 '18 at 06:06

Mohammed Jafar

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score 0 · Answer 3 · answered Jan 27 '12 at 09:45

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For better security I know that doing this is not good thing - thanks for comments under the question. So better do that by CRON task, without any user access, right?

session_id($variable_PHPSESSID);
session_start();
unset($_SESSION['something']);

answered Jan 27 '12 at 09:45

Lucas

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php - Is this possible to unset one variable from other session?

3 Answers3