sending untampered information

[mcirsta]

Ok , I need the user to click on an image and then to be redirected to a site where I can pick the data clicking on that picture provides ( IP , host ) . (for traffic loging / redirection )
How do I make sure the user really clicked on that image and not just typed it in or whatever .
I could encrypt it but then he/she can see the key , because he/she must have access to the php scrypt on his/her site , right ? Can I somehow get those log adresses like at hotmail which only I can decript and know if they are valid or bogus auto generated ones ?
Thank you !

[Weedpacket]

Perhaps start a session on an earlier page (doesn't matter too much what information you put in it - you'll think of something). Instead of providing a link directly to the image file, link to a script which first checks to see if that session is present; if -and only if - it is, then the script can server up the image data.

[mcirsta]

So data that I put into a session will last for as long as a browser is opened , right ? It will be there even if I go to another web page .
This is very useful , thanks .
Is there also a way to check where the user came from without any special php coding in the page where he came from ? ( like if he visits www.mypage.com and clicks on a link www.homepage.com/detect.php , can I see in detect.php that he came from www.mypage.com ? ).

[Weedpacket]

For your first question, look into PHP's [man]session[/man] handling facilities. For the second, look at HTTP_REFERER (details on this page).

[mcirsta]

OK , I really apreciate the help .
Thank you !