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Re: how to unset session variable when leaving page [message #174742 is a reply to message #174739]

Fri, 01 July 2011 12:00

Denis McMahon
Messages: 634
Registered: September 2010

Karma:

Senior Member

On Fri, 01 Jul 2011 05:36:55 -0400, Jerry Stuckle wrote:

> On 6/30/2011 11:41 PM, Martin wrote:
>> On Jun 27, 7:48 pm, Co<vonclausow...@gmail.com> wrote:

>>> [how do I clear a session when leaving a page]

>> [onunload javascript event calling a server side script]

> Which is not at all reliable. Better to code the server side properly.

Yes it's unreliable, and in this case there is a server side solution
(after all, the server knows which page is being requested, and the
referring page, and the contents of any post or get data, so in this case
there is a server side solution).

However, concerns about relying on javascript aside, using an unload
javascript event to call back to the server when the page is unloaded is
as far as I know the only active method that can be used to signal that
the user has browsed away from a web page, as opposed to passive methods
based on session timeouts. Yes, I agree that it is not perfect, and it
needs to be backed up with a session timeout anyway, but it's the only
mechanism that provides for even a chance of the visitor's browser
actively telling the server "byebye".

Unless, of course, you have a better method to suggest to us.

There is I believe another flaw in the logic that underlies the OP's
code, and it's a flaw that caught me out when I started using sessions.
He needs to consider the possibility that his visitor will have multiple
pages from his website open at once in different tabs, and these will all
be part of the same session.

Thus it is possible for:

request page 1 from google search [lastPage = null, ref = google]
request page 2 from page 1 [lastPage = 1, ref = 1]
request page 3 from page 2 [lastPage = 2, ref = 2]
request page 4 from page 1 [lastPage = 3, ref = 1]
request page 5 from page 2 [lastPage = 4, ref = 2]

If he is tracking the current page in his session data contents, then at
the point page 5 is requested, he may be assuming the visitor is coming
from page 4 unless he also tracks the referrer at each request. I didn't
see any indication in his code that he does this.

Of course, it may not matter, but then if it doesn't matter, I wonder why
he's worrying about the issue of unsetting session data when the users
browses to another page anyway.

Rgds

Denis McMahon

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[Message index]

		how to unset session variable when leaving page By: Co on Mon, 27 June 2011 18:48
		Re: how to unset session variable when leaving page By: Martin on Fri, 01 July 2011 03:41
		Re: how to unset session variable when leaving page By: Jerry Stuckle on Fri, 01 July 2011 09:36
		Re: how to unset session variable when leaving page By: Denis McMahon on Fri, 01 July 2011 12:00
		Re: how to unset session variable when leaving page By: Jerry Stuckle on Fri, 01 July 2011 16:35
		Re: how to unset session variable when leaving page By: dougatmilmacdotcom on Fri, 01 July 2011 11:50
		Re: how to unset session variable when leaving page By: Peter H. Coffin on Fri, 01 July 2011 21:58
		Re: how to unset session variable when leaving page By: Martin on Fri, 01 July 2011 09:01

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