php - How can I count valid clicks for my ads? -

i build own advertisement system. want user able specific amount, 5 cents, each click ad gets.

but facing problem. don't want users click bomb ads earn more. want count 1 click per user per ad.

this have come far ...

<?php  $ip = $_server['remote_addr'];  $query = mysql_query("select * user_ip ip = '{$ip}'");  if(!isset($_cookie['ad_click'])){     $_cookie['ad_click'] = 'ad number'; }elseif(mysql_num_rows($query) < 1){     mysql_query("insert user_ip (ip, time) values ('{$ip}', " . time() . ")"); }else{     // ad 1 more click user account }  ?> 

my main problem people can delete cookies , change ip address. won't work in real world.

there's no perfect way identify user, there enough imperfect ways that, if use them can make pretty guess.

• ip address should first thing check. ip stay same during single session , weed out layman trying clickbomb.
• user agent tell browser , os

on client side there's lot can do. check out evercookie:

• standard http cookies
• http strict transport security (hsts) pinning
• local shared objects (flash cookies)
• silverlight isolated storage
• storing cookies in rgb values of auto-generated, force-cached pngs using html5 canvas tag read pixels (cookies) out
• storing cookies in web history
• storing cookies in http etags
• storing cookies in web cache
• window.name caching
• internet explorer userdata storage
• html5 session storage
• html5 local storage
• html5 global storage
• html5 database storage via sqlite
• html5 indexeddb
• java jnlp persistenceservice
• java cve-2013-0422 exploit (applet sandbox escaping)

pay attention unusual click frequency , strange patterns.