The solution outlined below is believed to be obsolete & ineffective, but retained for historical interest. Phorm have changed their method of operation to hi-jack image requests. You should encrypt your web communications using SSL.

Server Dephormation

This is the server side equivalent of the Dephormation Add On for the browser.

It sets a Phorm OPTED_OUT cookie in the current domain, and erases any UID cookies set.

Installation

Simply copy the code into your web space, and place the PHP script as an image on as many pages as possible in your web site; 

<img src="/server/server_dephormation/dephormation.php">

Download Server Dephormation Here

Zip archive is here to download.
Current md5sum 42c0088b04d8298735a2511a24d59737

Tar.gz archive is here to download.
Current md5sum ea2993221bfb423edc393e7eeae1e0c2.