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Posted by Matthew Weier O'Phinney on 09/28/31 11:14
* James <jtu@esidesign.com>:
> I apologize in advance if I'm asking basic questions...
>
> When you hit the back button, won't the browser just take the page
> from the cache?
>
> I haven't switched my POSTs to GETs and this is what I'm seeing.
> I have a list of images. There are check boxes next to the images.
> When the user checks images and clicks on a DELETE CHECKED link, a
> new list is shown (minus the ones deleted.) When the user hits the
> BACK button, I see the list again with checks next to the previous
> images marked for deletion
By the way... the rule of thumb I think about is this:
* Use GET requests when you want to be able to bookmark the page --
i.e., when you want the behaviour repeatable. Typical example is
searches.
* Use POST requests when the operation will affect the data in some way
that shouldn't be cached. Examples: submitting data that will be
stored in the database, will update a database, or will delete an
entry in the database.
Because of the back button issues (namely, not all browsers treat 'back'
the same way), you will need to do some workarounds, typically with
sessions; I've mentioned these under separate cover.
> Just in case...
> I tried to add the following header before any html output to force
> the browser to not load from the cache and it didn't work.
>
> header("Cache-Control: no-store, no-cache, must-revalidate");
Not all browsers will actually follow these 'rules' (actually, they're
in the HTTP specification, but 'rule' just sounds better). Heck,
versions of the same browser on different platforms sometimes treat them
differently.
This is why session handling techniques are a common 'fix' for bad
browser behaviour in these instances.
--
Matthew Weier O'Phinney | WEBSITES:
Webmaster and IT Specialist | http://www.garden.org
National Gardening Association | http://www.kidsgardening.com
802-863-5251 x156 | http://nationalgardenmonth.org
mailto:matthew@garden.org | http://vermontbotanical.org
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