Cookies? Prevent multiple responses by individual user

artnow

Hello All

I am having a logic crisis. I am having users sign up on my site to receive an email quiz. The email quiz question contains a unique URL for that user that includes their email address, first name and the quiz id. The landing page automatically imputs the name, email and quiz id into the answer form and when submitted, all the info is written to the database. Users are only allowed to answer each quiz question once.

The problem is that some users are registering using different email addresses and names (based on ip). The result is that the same computer (again basing it on ip) answers the question more than once.

How would I resolve this? I believe cookies might be the answer but I am not certain. I know that IP tracking is not reliable (AOL for instance) and after reading the info at PHP.net about cookies I am not sure if that is reliable as some browsers present problems for cookies.

Thanks

Bob
Webmaster and PHP Newbie
WackyTaxi.com
http://www.wackytaxi.com

morphy_6deex

mmm
there is always a way to go round that... in italy any person has a unique code (codice fiscale) and a registered user must enter it in some systems... but there r generators of this "codice fiscale" so... there is always a way to give multiple answers, i suppose... cookies r one more check to get harder these escamotage...

ip is not good because my brother wants to answer from my machine... accounting... but people can use more emails... etc etc etc...

dalecosp

How reliable do you need it to be? Cookies might work. You'd want to code the thing so they couldn't take the quiz until one was set, and set it so the expiry date was far enough into the future that it wouldn't matter again. Of course, the real bstrds will erase their cookies and come back, right? And, then, some folks will be disappointed 'cause they can't take the quiz...how much of a PR issue is that?

IP verification has one problem: what about multiple users on a local LAN, using NAT, show that they all show up at the same IP? I'd think this would be a large percentage of users these days...for example, my kid, my wife, and I would all show up at the same IP, though we each have a box...

/me decides I need to study 'sessions'....

artnow

As I was coming here to reply to your answers I noticed another newbie question regarding sessions. I will need to read up on it but from what I have gathered this may work well! Thanks!!

jnuneznyc

You can't based it on IP because companies are using NAT to allow their employees to access the internet. So if you send a user in a company of one hundred an offer they will share it with a few friends and they will each create unique accounts but it all be coming from one IP address because the way their network is set up. Currently at my home the Playstation 2, Mac, Linux and Windows boxes share one IP address from my ISP because I have a DLink Router with 4 ports.

Cookies who be your only option but remember. A user can always delete his cookies and create a new yahoo mail account.

dalecosp

Originally posted by artnow
As I was coming here to reply to your answers I noticed another newbie question regarding sessions. I will need to read up on it but from what I have gathered this may work well! Thanks!!

Yeah, I think that's what sessions were invented for....let me know how it goes...I need to learn this stuff, but it seems I'm so busy.....