I would like to place an image on a site, or my forum signature for example (just an example) and be able to keep record through a mysql db of referrers or the page it loaded on...

My friend at browserreports.com does it to track user agents and stuff for his browser stats but I haven't talked to him in a long time. I want to be able to track what pages my image is being loaded on and how many hits it is getting as well.

How would I do this? What should I look for on php.net?