On Jun 30, 2009, at 10:59 PM, Paul M Foster <paulf@xxxxxxxxxxxxxxxxx>
wrote:
On Tue, Jun 30, 2009 at 06:38:19PM -0700, Mary Anderson wrote:
Hi all,
I have a php application for which I have a page which creates
temporary junk and puts it into a persistent store (in this case a
postgres database, but that is beside the point.)
I have a Save button which puts the stuff I really want into the
persistent store and cleans up the temporary junk. I have a Cancel
button which only cleans up the temporary junk.
I would really like to have the cleanup code run anytime a user
leaves the page without hitting the Save button. Is there anyway
to do
this? I.e. have php code called conditionally on exiting the page?
If the user hits the "Back" button or exits via clicking on some
link on
the page, there's no reasonable way to do this (Michael's cron
versions
excepted). Because the HTTP protocol has no effective memory,
there's no
way for it to know that the user exited without saving. You can do
various tricky things like set a $_SESSION variable, and then have it
checked at the top of each page where the user could go, and check and
clean up if the variable has a certain value. But that's pretty
tedious.
You could execute the whole thing as part of a class, and put a
check in
the constructor of the class (where it will be called on every page)
which cleans up if necessary.
In other words, there are ways to do this, but they are tedious. The
PHP/HTTP execution engines have no way of doing it on their own.
(Oh, there may be a way to do this with Javascript. I'm not good with
Javascript, but maybe there's some "OnExit" event which you could
use to
cause a Javascript function to do an AJAX call to a PHP script which
cleans up. I dunno.)
Paul
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Paul M. Foster
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The js function Onunload() could do that but there is the issue if the
user hits the back button, or moves to another page.
It's the same issue as the standard logout button. Users don't have to
trip this to leave the site, closing the browser or moving to another
site creates the same issues.
Doing the clean up via a cron is prolly gonna be the best option
Bastien
Sent from my iPod
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