I just recently created a new site for a client and he decided he wanted to do PPC. I created a landing page for him. I still wanted the users to be able to see the rest of the site but I wanted to show a specific phone number to PPC visitors. I created some PHP code that gives a 10 year cookie to anybody who hits my PPC landing page. On every other page in my site I put in some code that checks for that cookie and gives then a PPC phone number if they find that cookie.
Code for PPC landing page. Must be very first thing on page.
setcookie("ppc", "this works", time()+60*60*24*365*10);
Code for every other page.
echo 'ppc info';
echo 'non ppc info';
You can use that code to display a different logo or image with phone number in it or special text. If you have your phone number all over the place I would put your phone numbers in different include files so that you can change them easily.
Code for include
[tags]ppc, php, adwords, SEM[/tags]