CODEWITHSUNDEEP
javascriptphpsql
Erik Nucibella
Erik Nucibella

Reputation: 121

How to set offline a User in the DB when it closes the browser?

i have a logout function that sets the User offline in my DB (mysql), but if it just closes the browser, in my DB the User is still online despite it's not , How can i manage this? How can i set the User Offline without press the logout botton? Cheers in advance !

Ps: Yes, i'm using SESSION

Upvotes: 1

Views: 1356

Answers (4)

ArtisticPhoenix
ArtisticPhoenix

Reputation: 21681

HI the only reliable way is to set an interval that calls the server and logs it in a database 

 var timeout = 15000; //milliseconds
 setInterval( function(){
       $.post('yoursite/keepalive' ); 
 }, timeout );

Then you check the session on the server side you need a simple database table with the user id and a timestamp of the last time keepalive was called, then you just get the current time an there id ( from the session ) and save that. Then you can check if its been more then say like 20 seconds you will know they are gone ( should be updated every 15 sec ). Obviously you would need to have this interval on every page of your site to accurately track a user.

Things such as checking the session time, and unload are not accurate enough,

Unload is fired when any page is closed, so for example, we have a user that has 2 pages open, they close one of them. the other page is already loaded so there is no traffic between client and server, and no way to know that page is still open

for Session time we have a similar problem, say someone is reading a long post on your page, They need to use the facilities and leave the page open. 30 minutes go by the come back and continue reading the post for another 10 minutes. now maybe the session has expired maybe it hasn't the fact remains they are still looking at your site, and you have no way to know it.

An interval will continue as long as the page is open and there are no javascript issues. A disadvantage of this is it will also keep their session updated ( you can get around this by sending the user id along with the ajax and not using the session, but that has other complications ) because you have that 15 second update you can check anytime if it has been more then 15 seconds. Say you want to display a list of online users to your other forum users, you just query for everyone with a current timestamp from that table, easy beazy.

As for the amount of time for the interval, you have to strike a balance between performance ( network traffic ) and how granular you need to know the information, if it's ok to only know if they logged off within the last minute then use that, if you can wait 5 minutes to know etc....

Really the Crux of the problem is how the server, and a client communicate. Right there is no two way communication like if your on the phone. It's more like a walkies talky where you have to say 10-4 and let go of the button for the other guy to talk. Essentially a client will make a request, that request is fulfilled by the server. that is the end of the communication and the state. Subsequent request state is maintained by using session so the next request uses that session to 'remember' the client. other then that there is no communication between client and server. There is no way to know they hung up the phone, for example, but to ask them if they are still there. ( this is an oversimplification because you cant send a request from the server to ask, more like they have to tell you they are not there, unless you use node.js or something like that ).

As @David has mentioned you could track this based on last activity, for that you would just need to know when the session was last updated. One of the easiest ways is to move the session into a database handler via http://php.net/manual/en/function.session-set-save-handler.php that way you can access when they were last active.

Using this vs ajax really depends on what you need to know, and how accurately. There is also the content of your page to weigh in. If you have a site that makes requests frequently it would be a better approach because you save on network traffic, for example. However, if you have long post someone could be reading for 20-30 minutes but want to know more frequent then that use ajax.

Upvotes: 1

user3690350
user3690350

Reputation: 11

You can do it in following ways. 1) send the Ajax request to server every 5 seconds to update the current time. 2) and where you want to show offline just get records where current time is more than 5 seconds ago.

Upvotes: 1

Eduardo Escobar
Eduardo Escobar

Reputation: 3389

You can try the javascript beforeunload event:

window.onbeforeunload = function() {
    // Some AJAX request to logout.php or whatever script handles the logout
}

It will trigger when the user attempts to close the current window.

Watch out though, even if the user closes a single tab (your page), the event will be triggered, so if there are other tabs opened, so the browser will be, and you'll still get your users logged out.

Also, if several tabs of your website are opened, and you close one of them, you'll get your users logged out, which may not be what you want, so you'll probably have to find a way around to fix it.

Upvotes: 0

napolux
napolux

Reputation: 16094

You can do it in many ways:

  • Launch an AJAX call on onbeforeunload javascript event. Prompting for a confirmation "Windows is closing, are you sure? YES/NO" should give you enough time to set the flag in the db, just be sure that if the user clicks "NO" you should unset your flag
  • Check session time... Add a var in your PHP_SESSION that is updated at every user event. If it becomes older than a preset threshold (i.e. 5 minutes), you can safely assume the user is gone

Example for onbeforeunload

function myConfirmation() {
    return 'Are you sure you want to quit?';
}

window.onbeforeunload = myConfirmation;

Upvotes: 0

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