How to create Tracking Pixel

[jtwalter]

I have a page on another website that needs to be tracked. Basically the user signs up on our site, and then ends up on a "thank you" page on the billing company side. So the only way to track user conversion is by being able to track this "thank you" page. I thought I could do this by having them place a piece of code that I wrote of a 1x1 iframe to a page on our site, that way when this page has a view, it means someone ended up on the "thank you" page. However, this iframe misses some views sometimes (if anybody knows why, please let me know). We know this because we can see the amount of signs up from the billing company. I have seen the use of tracking pixels and can't figure out for the life of me how they work, nor can I find anything online. It's a code such as <img src="http://www.mydomain.com/pixel.php?signup=1234" width="1" height="1" />This must be better somehow than the iframe that I put in, because all advertising companies we have worked with use this. Do you know what kind of code would have to go into that 'pixel.php' page? Thank you very much!

[Ingolme]

It just gets user data and possibly sends a cookie. You can find user data in the $_SERVER array and send cookies with setcookie(). It uses the GD library to display a transparent pixel in GIF format.