Track How Far Someone Scrolls Down on Web Page

We have a website whose main page is a long sales page -- about 45 scrolls to get to the bottom -- that attempts to sell someone a product. We want to be able to track how far down a visitor scrolls when they view the web page. If there's some way of putting anchors in the text that automatically trigger some command back to our servers that notifies our servers that that portion of the webpage is now viewable, that might work. Perhaps there is some command in javascript that you can use to trigger this call back to our servers. The only part of this project that we need done is the front end code that sends a communication back to our database. We are currently using PHP on the front end with a MySQL database, and we want this to be database-driven; meaning, whatever code you come up with, it should send a message back to our database. We have another programmer who can then modify our database to correctly log whatever information is being sent back so we can track how far the average person scrolls down. So, you simply need to tell us something like: "Install this code for each anchor you want to record in your web page and create a unique tag for each one so you can differentiate each one in your database. We've seen other people do something like this, but their code requires the user to hover their mouse over each area to trigger the tracking; we want to have the tracking triggered by the scroll, not the mouse hover, since many people just use the scroll bar and leave their mouse there and read the page. Hopefully this is enough information to understand what we need; however, please feel free to ask any questions if you need any clarifications. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). 4) Payment will be remitted once we've tested and confirmed that the code logs everything correctly. ## Platform PHP with MySQL on Linux