Determining origin of traffic from Referrer Header characteristics

I'm writing a web application that will track incoming traffic to a website and track the origin of the traffic and its behaviour on our site, so that we can get some idea of the return on investment of our marketing campaigns, the actual keywords and their value to us (rather 开发者_StackOverflow中文版than to google) and the lost traffic, and our lost spend.

Part of this involves looking at the referrer information from the browser on the first page visited. Referrers like Google Organic and Google Paid Search are easy to identify using regex matching to look for particular strings within the referrer (I'm using php's $_SERVER). The same is true for Bing, Ask, Yahoo, LinkedIn and Facebook.

But, I'm having a problem with one particular source - Google Content Network. Sometimes traffic coming from these ads has a nice link that begins http://googleads.g.doubleclick.net/pagead/ads? which is obviously easy to code for. On the other hand, the traffic from sites showing our ads sometimes comes with the Referrer of the site itself as though it were a hard coded link. This second hard coded type link is causing problems as we can't differentiate it from regular referred traffic.

So, other than tagging the urls our ads are pointing to with something like '?source=gcn', or scraping the referring page to look for a hard coded link or a google ads iframe, has anyone got any magic sauce to overcome this issue?

Thanks in advance

Ross

So, it seems I've been looking in completely the wrong place for a solution to this.

In a nutshell, the problem is that I need to access Google PPC information regarding visitors to my site but google doesn't always pass this information along in the referrer and certainly is problematic where Display Network appears on a page using javascript to insert it directly into the dom.

Where should I have been looking? Google Analytics. The __utmz cookie contains a wealth of information regarding the route that traffic got the site... including whether they came via PPC / Organic or Display Network and the search terms (where applicable) that got them there.

See the following page for more information:

http://code.google.com/apis/analytics/docs/concepts/gaConceptsCookies.html

Who'd have thought! Anyway, there is some great documentation on what the cookies do and how they are constructed. Problem Solved.

Ross