On Session End

[Anon]

Is there any easy way that when a session is ended, I can have a script/function run?

The id of a shopping basket on my site is put into a session variable. Once the visitor leaves, they can't get back to it, and when they return , a new basket record is created.

When the session ends (is this about 15 mins? - how do I change that?), I want it to delete the records associated with that basket (unless the order has been paid for, in which case they're needed).

In ASP, I'd have a Global.asa file in the root, which would have an On_Session_End function, which would be run each time a session is ended, and I could have some sql to delete the records.

Looking at the manual, I have to change all of the handlers

session_set_save_handler ("open", "close", "read", "write", "destroy", "gc");

which I don't really need.
It also says I gotta do my own garbage collection... I just wanted something simple!! 🙁

[[deleted]]

"Is there any easy way that when a session is ended, I can have a script/function run?"

No. Sessions never end, they just time-out, they become unused.

PHP's session handler will timeout the session for you, and force the start of a new session.

All you have to do is create a crontab entry or something like that that starts once a day, to clean out the database.

[Anon]

I was thinking of that, but it someone's at the site at the time, it might screw something up.

Since php cleans up (or I assume it does!) the session files when a session times out, I thought maybe it'd be able to run my function too?
Otherwise, I've got a database record for every single session, when only a fraction might actually buy something 🙁

[[deleted]]

"but it someone's at the site at the time, it might screw something up"

No, because one person can use one session at one time, so either they continue on the current session, or they get a new session, leaving the old session for dead.

PHP does not have any function you can trigger when a session times out. it would be nice, but HTTP is stateless, PHP does not run continuesly. MS 'solved' that by making ASP run all the time in the bacground waiting for the session to time out. But MS have holes in their heads....

[Anon]

vincent wrote:

"but it someone's at the site at the time, it might screw something up"

No, because one person can use one session at one time, so either they continue on the current session, or they get a new session, leaving the old session for dead.

If someone had stuff in their shopping cart, and I clobbered the db record, when they next hit a page, the basketid in their cookie/session doesn't exist in the db, and their basket will have emptied.

vincent wrote:

PHP does not have any function you can trigger when a session times out. it would be nice, but HTTP is stateless, PHP does not run continuesly. MS 'solved' that by making ASP run all the time in the bacground waiting for the session to time out. But MS have holes in their heads....

So how are the session files deleted? I wanted to link it that 🙁

[[deleted]]

"If someone had stuff in their shopping cart, and I clobbered the db record, when they next hit a page, the basketid in their cookie/session doesn't exist in the db, and their basket will have emptied"

And if the session has expired, PHP nolonger knows which DB record to use to fetch the basket's contents, and you will create a new basket.

"So how are the session files deleted? I wanted to link it that 🙁"

PHP checks the 'last update' date of the session file whenever it is opened. If the file is older than the max lifetime defined in php.ini, the file will be ignored as garbage.

The file is deleted by the garbage cleaner that will erase all files that have expired. But, the cleaner does not run on every session_start because that would take too long, and make no sense anyway. Instead, the cleaner is executed with a certain probability, you can define the 'chance' that the cleaner will be executed.

[Anon]

vincent wrote:

"If someone had stuff in their shopping cart, and I clobbered the db record, when they next hit a page, the basketid in their cookie/session doesn't exist in the db, and their basket will have emptied"

And if the session has expired, PHP nolonger knows which DB record to use to fetch the basket's contents, and you will create a new basket.

While people are moving around the site, I wanted them to keep an id in the session, once that session has expired, it should be deleted, so next time the return to the site, they'd get a new one.

I've changed it now anyway, so it uses a cookie, set to expire one year on. Ok, people clear out cookies, but the number of redundant records will probably a lot less than if they all stayed.

I've also changed it to only create the record in the database when the user puts something in their basket, so the people who are just browsing, won't add masses of records to the database.

[bltesar]

Vincente wrote:

PHP checks the 'last update' date of the session file whenever it is opened. If the file is older than the max lifetime defined in php.ini, the file will be ignored as garbage.

The file is deleted by the garbage cleaner that will erase all files that have expired. But, the cleaner does not run on every session_start because that would take too long, and make no sense anyway. Instead, the cleaner is executed with a certain probability, you can define the 'chance' that the cleaner will be executed.

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because there is some mechanism by which sessions are expired, then there must be something running in the background managing this feature. Whether or not it is running continuously does not matter. A session is either exipired or active, and sometimes we might want to perform some tasks before it is destroyed. Theoretically, whatever mechanism expires sessions should be able to trigger some functions to run before the session is destroyed. Either this feature was just never implemented in PHP or we are just unaware of the how to access it. Obviously, the latter choice is unlikely. Such a useful feature would likely be widely known.