Currently when the user logs in my site, a (PHP) session is started and his database row is saved in his $_session. I do so because the size of user's data is small for now, and this way I do not have to ask the database for user's data every time I need it.
The problem is that, when I want to add or change something during the development and I touch the database, the session is not updated this way. The user have to logout and login again to update the session. This is good for now since the site is in development phase, but in production this is not desirable.
I wouldn't delete session files, because people are lazy and I would avoid to force them to re-login every time something change in database, and I do not want to reload the session every X minutes. My solution for now is a boolean column inside the user's table, false by default, that I set true when I change the database. Every time a session is continued, session data will be updated if that value becomes true. Anyway this way I have to do a (small) query every time an user continues a session. I do not know if this will be a problem in production.
Is there an alternative / better way to solve my problem?
If I understand the problem correctly, one way to handle this would be every time a user row in the DB is updated that user's session data could be updated as well in PHP.
If it is not the user updating the records (such as an administrator changing a user's permissions) most likely you would want to force a logout of the user. If it is the user updating the records (such as changing information in their user profile) simply updating those values in the session variables may be enough.
In both of these cases you probably also want to provide a message to the user letting them know what happened.
Related
I'm currently using PHP sessions to keep track of user sessions, with a last-activity field for timeouts, an id field, and an account-type field. Currently, all of this information, as well as settings data, is pulled form a MySQL database and stored in the session once the user is logged in, and remains unchanged for the duration of the session.
The issue is that I wish to implement the ability for administrators to change users' account types remotely. If the user's account type is changed remotely while they're still logged in, the change in the database won't be reflected in the user's session variable.
One solution to this would be to add a logout_flag column to the users database table. When a user's account type is changed by an administrator, that user's entry in the database will have logout_flag set to 1. Then I can use a session script to check this entry on every page load, and log them out if it's set to 1.
My concern is that this would add too much overhead for the server; With hundreds of users logged in at the same time, this would amount to hundreds of MySQL queries per minute. Is this the ideal solution though?
Try with session_save_path(), with that function you can find the path where PHP saves all session files. You can delete the selected file with unlink() later.
Careful with this! If the path = the global /tmp directory. Other applications are using this directory also and you can break something.
You need to know also the session id of your user, maybe saving the token and the user id/name will help you to identify the correct session file.
I have a system that represents users as object. These object are initialized by reading in a database. Once the users (or objects) are created I store them in a session in order to navigate through pages without re-initiate the users from the database.
Suppose that an admin changes (let say) the users' permissions. From the edit until the session expires, a user could have higher (or lower) permissions than those declared by the admin.
How can I handle this kind of situation? Suppose I have a sessions that expires after hours or more. Should I send a request to database every n minutes to update the user objects?
The way I do it in my applications is a check on every page load.
So, permissions might be stored in a session, but you can always update those.
Let's say someone logs in and their permissions are set to full.
If you're checking on every page load and updating their session, someone can update their permissions at any time and their object will have the new permissions reflected every time they perform an action.
It doesn't matter much if they're just reading a page, but when they try to do something: submit a form, go back to home, visit a new page, or whatever, then their permissions will get updated.
I'm developing a site in PHP. When the user session starts I load all his db row in the $_SESSION var. When the user changes a db value I update the $_SESSION var too.
The problem starts when more than one session is active for the same user. Is there a way to update the data for all the sessions of the same user without overloading the database? Or, alternatively, is there a way to force php to use the same session file for all the session that belongs to the same user? Or I must simply query the db every time a session continues?
And another dilemma is: is it worth it? I mean, I do not know how much this mechanism could alleviate the server load, and I do not know if this mechanism is applicable to file-based sessions or I must use another session storing type.
This question is somewhat related to this other question on mine (even if the workaround for this is simply to delete all session files).
It really reaches the question why would you need to many data in a $_SESSION. And you should really take a time to decide which data is so often needed to be displayed.
In most of the cases you only need session identifier that keeps the user logged in, containing user_id, to take the needed data directly from the database.
Assuming the user can change its avatar, and you haven't go so many places to display this avatar, you don't need to store it in session, nor to SELECT it at the very same time. For instance, you can have a trigger page, which SELECTS the avatar by $_SESSION['user_id'] when he tries to send personal message to another user. Otherwise, you can put a cache (i.e. using memcached) where a query, which selects the user avatars should not be made more often than once an hour.
If user changes an email, it's the same. If somebody else tries to send him message, you trigger the SELECT query. Otherwise a cache is set.
So, let's say the user has changed his avatar, email, some other trivial info, then accessed your index page. In his session you load only the identifier. In the db the records are present, but they are not selected yet. So you have neither server load, because the session is light, nor database load, because no SELECT queries were sent.
No matter how many times the user tries to set his session (in this case logs second time), you have a present data in the db, and a session only with identifier. You can identify all his instances, but never use a data, which is not needed.
1 Well, I (don't, but) could do this with my session handler. I use databased SESSIONS with some extra information/columns like username and userid. That way I can exactly determine which session belongs to which user without fiddeling around with the serialized data.
http://php.net/manual/de/function.session-set-save-handler.php
2 But in your case it might be simpler to update your user table and then SELECT the user again to put the (new) data to $_SESSION['user']. (You will need some "user data was updated" info, to reload new data for all sessions).
3 Or you just avoid that a user can login more than once.
I'm storing some user information in session so I don't have to query the database every single time user changes page. What if this user uses multiple browsers/computers and olders sessions have invalid data now? How do I keep them in sync? Logging out the older sessions of the user is fine, but I would like to avoid writing session info to db, if possible.
I do realize it's a fairly common problem, but I couldn't come up with right stuff after googling.
Store the session in a database for each specific user.
Then each time the users access your site (regardless of which browser) - all the information is always in one location, and you dont have to do any fancy 'sync' stuff.
Note: they will still have to 'login' from each different browser. During the login process, you will need to check if a session already exists in the database for that user. If it does, you need to attach this new login to that session (rather than create a new one).
I'm working a site where users could technically stay logged in forever, as long as they never close their browser (and therefore never get a new session key). Here's what I could see happening: a user leaves a browser open on computer A. The then use computer B, login and change their name which is stored in the session. They logout of B, but A is still logged in and still has their old name stored in the session. Therefore, their name won't be updated till the next time they logout manually or they close their browser and open it again and are logged in through the remember me function.
Name is a simple example, but in my case the subscription level of their account is stored in the session and can be changed.
How do you deal with this?
A few ideas that I have are:
After a period of 10 minutes or more, the session data get's reloaded. It might be exactly 10 minutes if the user is highly active as the function will get triggered right at the 10 minute point or it could be after 2 hours if the user leaves and comes back and then triggers the functionality.
Store as little information as possible in the session and load the rest from the DB on every page call. (I really don't like this idea.)
Use database sessions and use the same session on all the computers. I like this, but I could see it getting confusing when something like search criteria are stored in the session--the same criteria would show up on both browsers/comptuers.
For information, even such as the user's name or username/email address, store it in the session, but for other information that would heavily affect their abilities on the site, don't store it in the session and load when needed (attempt to only do it once per instance).
Are there other better methods?
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Another option: 5. Use database session and when an update is made load the user's other sessions (just unserialize), change the relevant information and save them back to the database.
I would go either with number 1 or number 4. If you store the time of the last update of the information, you could even ask on every request whether the date has been updated.
Don't store information likely to change in the session, if you're looking at scenarios like the one you outline. Just get over your dislike of loading user data with every page - it's by far the best idea.
I'm guessing you don't want to load the data from the database because you're concerned about performance issues somehow. Before you try out any of the other solutions, you might want to test how long it takes to actually load a users data from the database, then check that against your number of users - chances are you won't see any performance problems due to loading user profiles on every page.
Regards
I'd go with option 6: only store userid and session specific stuff (search criteria) in his session and put the rest into APC/xcache (memcached if you're using multiple servers).
this way you'll only have to go to the database the first time (and after the cache expires) and you can still share any data between users sessions.
Normally you should do 2), but you don't like it.
maybe you can use sessions stored in db.
when a user change his name, put into all sessions from that user the information "refresh userdata".
on the next request the userdata is reloaded again into the session and is cached there.
this can be done be reusing your loaduserdata function which called at login.
php session_set_save_handler() - also read comments
php session_decode() - to read the username from the session to store it additionally to the sessiondata. usefull for easily to find the users sessions for updating.
[edit]
don't forget:
when you are updating all the sessions while the page is generated (between session_start and session_write_close) you changes maybe lost.