php or something else for this

Anon

Hi. I currently have a website where users can upload ads to a classifieds section of the site. they put their information in over a series of 5 pages and finally hit the "POST AD" to add it to the database. My concern is that people who just want to goof off can hit back on their browser and click "post ad" again, and of course, repeat this process as much as they like until they are happy with their little bit of chaos. I have seen where some pages don't allow you to press back on your browser (ie, you press back, and that particular page just reloads)
is this a php question? can it be done with php? or is it pure html. either way, if anyone knows what Im talking about, please post. or, if you have any suggestions on how to prevent this that is a better method, let me know (ie, clearing the hidden fields, dunno.. )
thanks,
blue presley

Anon

Better method....
Set a cookie once posted, so they have to delete the cookie to repost it.
You'll have to make sure they can't turn cookies off though, ie they have to have accept cookies on in order to post.

As for stopping back button... well, Javascript has a great many functions in this regard, maybe something here, I'm not sure which though.
A method with javascript would of course be to open a new window to post, then just don't include the standard button bar :-)

Not sure if this works for IE and Netscape though.

Anon

Maybe you could check $HTTP_REFERER to be sure the user comes from the right page before returning the one with the posting button.
Another way is to look at the javascript "history" object; I think this is how the sites you mention do to prevent users from pressing the back button (they check if they are at the end of the history list, and if not, they go forward).

Anon

Additionally... you could have an intermediate page that inserts the data into the database and then calls <? header("foo.html"); ?>

So bascially what would happen is they would submit the data from the form page, go to some hidden page that would grab the data and redirect them to a "thanks" page. If they tried to hit back they'd just get bumped to to "redirector" page. Maybe you'd need two redirectors.. i dunno

Also, you could have a random "key" in a INPUT HIDDEN field on the form page... insert this into the database with all the other data, and just set a unique field on that field. perhaps and md5 checksum of something like the time+theirIP would give you a nice random key. They could submit all they want but it would only go in once.

Anon

The redirect pages...

Well, this is used on a PHP mb at planetarion, but it doesn't work well, you just either click back a few times, or right click on back and go back 3 or so pages 🙂

You could always ask them (or gamers.com) how the stop multiple posts, both restrict it to somehting like one every 30 secs, and gamers.com prevents multiple posts, just says its the same and stops it.

Anon

this might work,
on the posting page check for the refferer, if its other than the page in front send them back to the very start.
for each link to next page add the time() function result to the href link, doing this will force their browser to reload each of the submit pages rather than loading the cached version and because no values have been posted the value boxes should be blank.

anyone who wants to fill in all 5 pages again oviously has to much spare time on their hands.