So i'm using session variables to take the id of the user everytime he logs in. Just now, i realized that one of the problems i'm gonna face is that everytime a new user logs in, the value of the session changes. Is it possible that the session value (ID of the specific logged in employee) is not changed even if another employee logs in?
The sessions in php are client specific (browser specific) if a user logs in in one browser and another in second, there will be no conflicts in the variable as the first user can see his session id only.
Related
On a fitness website I'm working on, I use php $_SESSION to recall the user's username across the various php scripts that my pages use.
I had a tab open in Chrome that was logged in to one of my testuser accounts on a fitness website I was working on.
As I wanted to test the Update BMI feature on another user account, I opened a second tab and login-ed to another testuser account. The feature worked successfully, and my second user BMI was updated in the database.
However, when I went back to my first tab and tried the feature for my first user, it updated the BMI for the second user, not the first. This alarmed me immediately. I refreshed the page and realised I was actually now logged into the second testuser account.
This must be because a browser cannot store two different set of session variables. Is there anyway to allow a browser to do so?
Session variables are 1.
$_SESSION['user'] = 1;
So throughout your website, value of user is 1.
Now if you change the value,
$_SESSION['user'] = 2;
Whole website will have user value as 2 in session.
You have faced that problem because you have not refreshed the page.
Same browser cannot have multiple values for same variable, but its possible in different browser.
So 2 sets of value for same session variable is not possible in same browser.
Working:
Each session created will have an unique id , and that unique id is stored in cookies. Cookies in turn are store in browser. Every time you make request for session variables to server, it looks up for the session id in cookies.
Hope this helped you. Any doubt, you can ask.
A browser can only work with one session at a time.
However you can open another browser or use a private session(Ctrl+Maj+P) to test another session without loosing the first one.
I have a log in page which opens a profile page.Now when a user logs in the session is set.But i have not provided log out facility yet.So I can very well open the log in page and log in as a different user , without the sessions and cookies being destroyed.My question is when i log in the second time , which session does the browser use the previous one or the one which has been recently created.The profile page checks whether session is set or not.Can we have two sessions simultaneously for the same website.
Yup i agree with you SAM.
usually session user set for one user in one browser, and it will be automatic destroy by second user when login in same browser. I think it will be more configuration if you want two session with same value. for example facebook and twitter used one session simultaneously.
may be if you don't want destroy first session when second user login you can make function to check session is used or not.
Yes you can have two or more sessions you have to create with different names.
$_SESSION['user1']="some value";
$_SESSION['user2']="some value";
but if you are making only one session the new value will overwrite the previous one.
But it doesn't make sense why you want to login with 2 users simultaneously. You should provide more information.
i have a user login system which works off of sessions such that when the user logs in a session variable of user is populated with his/her username, then each page she loads checks this session, if it is not populated then the page is redirected to the login page. apon logout the session is destroyed.
But this still allows a user to open 2 different browsers at the same time and login. I want to stop this, such that if a user logs in and then trys to login using a different browser or pc, they get an error saying the user is already logged in.
So my first thought was to use a data base write, but then how do i know to unset that value if the browser is closed?
all my pages are php, and i use ajax and php scripts to update dynamic content.
So whats the best way to go about this?
they get an error saying the user is already logged in.
That's wrong approach, causing terrible user's experience.
Make it opposite: let that latter in, but make previous one logged out.
You only need to store current session ID in the user's table. If it doesn't match - ask for login.
If you find in DB that user is already logged in simply ask if he/she wants to go on and overwrite old session info. Another way may be adding a time-ticket to your database information (e.g. inserting time) and check how long is elapsed since inserted.
Regards
If I have understood your question properly, I think you can make use of cookie. Once user is logged in, you can create a cookie and set an expiry to browser session time. Before fetching data from DB, you need to check for cookie presence.
I would make another session variable that checks the browser type, if it is different call a view method to output what you said
I am developing the user management portion of a website that will host a webcast. The goal is to prrevent the same user nam (email address) from being used concurrently. That is, we don't want two individuals using one login to view the event.
I've already setup a table that holds the user registration data with regID as primary key. My thought is to create a login history table with username as primary key, foreign key to user name in registration table. The login history table would simply timestamp when the user logs into the site. However, this won't accomplsih my goal of preventing more than one individual from using the same login name.
Instead, would it be better to have a login status field either in the login history or user table that is set to 1 for logged in and 0 for logged out? It would need a stored procedure to update the value at login and at logout, and would need to be validated when a user logs in such that if login status = 1, user already logged in and cannot login a second time. Is this a feasible approach?
Please share other methods you've used to prevent the same login credential from being shared amongst multiple individuals.
Thanks,
Sid
If it is OK to logout an already logged in user if someone else logs in with the same credentials then you could do the following: when a user logs in generate a random ID in your database for that user and the same in a cookie session. The two must match to authenticate.
Without rolling your own session handler, you could do a little parallel tracking. When a user logs in, you can store the user's session ID and login time in the database (maybe inside the user information table). The login script could then check for the existence if this sessionID and allow/deny login based on the presence of the session ID. If the ID's null/blank, then the user logs in. If there's a session ID present, and it's more than X minutes old, allow the login. Otherwise deny them.
Of course, you'd probably want to roll your own session cleanup handler at that point, so that when stale session files get deleted, you can remove the associated IDs from the database at the same time.
The problem here is detecting the user is logged in (i.e. whether he didn't logout).
One possible way is to register in the database the time of his last activity and the time of his explicit logout. You could then deny a login if it this was attempted less than say 5 minutes ago relatively to his latest activity and if he didn't login in between.
You could force "activity" by having the website pages periodically poll the server with Javascript.
It's easy to determine when someone logs in. It's much harder to determine when someone logs out. If you have a mechanism of killing the webcast streaming to a particular user quickly, you might want to have something which pops up asking the user if they want to kill their other session if you think there might be one active.
How are you doing user sessions on the server? If you store them in the db, you could query the active sessions anytime someone attempts to log in and see if they're already in there. Of course you'd probably also have to check some kind of timestamp since you're not guaranteed that sessions will disappear at session.gc_maxlifetime.
You might want to consider making a global variable in php to store a hash array with login status. This has the benefit that if the application has to be restarted for some reason, the user isn't stuck in the wrong state in the database.
You can store a mapping from user ID to IP or session cookie and redirect requests that come with different information to the login page. If the user logs in, the other session would be invalidated and further requests in the last session forward to the login page.
how do you check if a user already has logged in?
so that if a user in another browser cant log in with the same account.
also, is this a good solution or should i let the user log in in the other browser and then log out the current user and display a message (you are logged in from another location) just like messenger does?
Using sessions is a good way to do this, and is a very common method for controlling authentication.
The flow usually looks something like this:
User visits site, and session_start() is called. A unique session identifier is set for that visitor (ie. a cookie).
User submits his login credentials to a login form
Login credentials are verified, and this fact is stored in the session data with $_SESSION['logged_in'] = true, or something similar
For the rest of the user's time on the site, you can check $_SESSION['logged_in'] to see if the user has logged in.
In order to control a user's logins, you could simply have a field in a database (users table is fine) indicating what the current session id is (retrieved with session_id()) for the user, and if it doesn't match the cookie value you just received, then you immediately call session_destroy() for that id, and consider the user as logged out.
Using $_SESSION means you don't have to worry about generating your own tokens, and gives you the power of the built-in superglobals to facilitate storing information about the user's authentication status.
Personally, I would allow multiple sessions to be active for a user for most web sites, as there's usually not a good reason not to, but it obviously depends on the nature of the site. However, storing the current active session id as mentioned above is a pretty simple way to accomplish this.
Generate a random token upon signing in (or use the sessionid), and store this in the database and in the users cookie. With each page access, ensure that the users token matches the database entry. If the two don't match, alert the user that they've logged in elsewhere.
You could also store the login time, which subsequently would be the time the token was assigned, and require 30 minutes before permitting another user to login with the same ID.
The first half of the question was answered well with how to detect the multiple users but how to treat them I think still needs a bit of work.
First if a user logs in correctly let them in, don't prevent them if they are logged on some other place. If you really don't want the user to have two open sessions then log out the old one or simply update the session id that you are saving so you can bounce out the old connection. You can inform if you want but I would only message the session that you invalidated. If you message the user logging in it becomes annoying when you are only dealing with the case of a user switching computers and they forgot to log out of the old session.
Well All solutions mentioned above will work but if on every page access you are making a call to database and checking for the session token to see weather its the same token assigned to user .. will kill your response time. what i'll suggest is use a caching mechanism instead of database in above said solutions. storing session token into database will add extra field to your database which is actually not required. Use open source caching solution like memcache.
you can make a table like userLoginStatus with fields like clockIn time & clockOut time,
and insert current time in clockIn when user is do login, leave clockOut time blank at that time, it should be updated only when user do clock over logout button,
so you can check specific user's current status, where clockOut is empty that user should be logged in. because it updated only when user do logout.