Getting previous url value into php

At my client site, a user can click a link for our "contact us" form from any
> page on our site. The contact us form is an HTML form that calls an php
> program which processes the form contents (ie, mails the content to me). I
> want to be able to track which original page the visitor was on when they
> clicked the "contact us" link.

Hi,
It is fairly simple. Within your form add an Input field, for its type simply call it "hidden," an allowable value and for text use your URL

<input type="hidden" text="index.html">

Peace,

Clarke