On Aug 15, 2011, at 2:11 PM, Philip Thompson wrote:

On Mon, Aug 15, 2011 at 1:43 PM, LAMP <l...@afan.net> wrote:
Hi all,
This is THE question that bothers me for a while... I always was keeping session info, like user ID, organization ID, selected book ID... within $_SESSION array. Main reason is to access and maintain it faster than keeping them inside session table. And, also, one less mysql connection. Though, in last project the $_SESSION grow up to around 30, even 50 elements of the array. And several people mentioned it's better to keep so big session data in mysql than in $_SESSION.

My question is pros and cons $_SESSION vs. mysql session. And, if the amount of data is only reason, when is better to keep all data in $_SESSION and when to store them in mysql?

Thanks for any help,

Hi all. Long time no see. I personally think 30-50 elements in an array is not a lot of data (unless you're storing hundreds of megs of data per element). You really have to weigh the pros and cons of using file-based session storage versus database session storage. With a quick google search, this article by Chris Shiftlett came up: http://shiflett.org/articles/storing-sessions-in-a-database . Specially look at the background section. It goes over a couple reasons to use a database. While this list is not exhaustive by any means, it should get you thinking. If the biggest reason for wanting to use a database over the file system is because of the space, then you may want to reconsider....

In file-based session storage, the session data is saved in a particular location (as specified in php.ini). So, if you have 10MB of data, this will be will stored in a file slightly larger than 10MB because I believe the data is serialized in some form. This file is accessed upon page load and is written to for the next page request. File I/O is generally pretty fast... generally much faster than database I/O.

In the database storage, you must run queries to pull the data necessary. This requires a connection plus the time to query plus the time to organize the data. If you have 10MB of data, then you still have to pull all of that from the database, so I don't believe you're getting any speed advantage. If you're application is running on multiple servers, then you'd want to consider the database storage. IMO, only use the database (for session storage) if it solves a problem that can be easily fixed otherwise by using file- based session storage.

Hope that helps,


I apologize for posting not-complete data :-)
The size of the data is, I believe, small. 1-2 words per array element or number. No image or something like that is stored in $_SESSION. I believe no more than few Kb.

My concern is not only speed, than handling (as you said "time to query plus the time to organize the data..."),as well as security. I read Shiflett's article but it dates from 2004 and I believe some stuff are changed too :-)

As I said, I prefer working with $_SESSION instead storing data into session table, but always wondered is that correct approach.


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