Confused about: unset($_SESSION[x][$type][$id])

Joseph_Sliker

Hi; The title says it all. Obviously I'm missing a concept here.

Say I allow a user to retrieve a bunch of their records, and they are placed in a $SESSION variable with a couple of dimensions (let's say $SESSION[x][$type][$id]=$record_facts;

I have the page display the values in a table by cycling through the session. On each line is a drop button (form) that allows the user to delete the record from the database (it passes the values $type and $id to a script to remove the item from the database. (feedback the the script worked and the item was dropped appears in a little iframe window for that row in the table) (all of this works fine...the record DOES get deleted.)

Here is the problem:
I also add the following into the script to remove the item from the $SESSION so that if the page is refreshed, the items will no longer show in the table (without needing to re-query the database every time.

unset($_SESSION[x][$type][$id]);

However this does not seem to do the job. Refeshing the page continues to show those records in the display table (even though the record HAS in fact been dropped from the database). So I guess I'm doing this unset($SESSION) thing wrong? I would like use $SESSION because the records are used in various other functions on the site during the user's visit...I just want to purge it of any records that they have decided to delete.

Derokorian

I would suggest reading from the database every time you want to display data from it, instead of storing it in a session. What happens when the session data is out dated because a row was updated?

Joseph_Sliker

Well, in this case, the user would not be able to update any records/rows...they are just records maintained by others to which a user might wish to select in order to keep track of (reminders of specific events or catalog items, for example).

I think I found a method that is sufficient for my purposes and easy for me to understand. When the array is created as part of the query process, I establish it in two forms:
$_SESSION[x][$type][$id]=$record_facts;
AND
$x[$type][$id]=$record_facts;

When the user clicks the button that deletes the database record, the $x[$type][$id] record is unset, and then I have the script also immediately overwrite the $_SESSION[x] version...this way, if the user navigates to another page where the records are used in some other context, only the remaining records will be displayed (without yet another trip to the database).

//...after the actual database delete record query, do this...
unset($x[$type][$id]);
$_SESSION[x]=array($x);

It seems to me that using sessions is a way to help a web application be as efficient/fast as possible, rather than to keep hitting a server with database queries.

laserlight

Joseph Sliker wrote:
It seems to me that using sessions is a way to help a web application be as efficient/fast as possible, rather than to keep hitting a server with database queries.

That depends on the session storage backend. By default, the session data would be stored in a file, so that will probably only be faster if the database is accessed over a network. The session data could be stored in the database, in which case there is no difference (other than it functioning as a database-backed cache with the right database indices).