Greenvy:
As your landing page url use: http://www.domain.com/page.php?keyword={keyword}
On your php page whereever you want to use the keyword use:
<?=$_GET['keyword'] ?>
If your too lazy to change all the urls your going to have to fiddle with the http_referer and parse out the keyword, more of a pain than its work
Edit: Damn its early, this whole thread is about what you are suggestingg greenvy
so correct if im wrong, if my domain was www.cookiejarz.com
i'll just have to change my ad site destination to
http://www.cookiejarz.com/page.php?keyword={keyword}
and use
<?=$_GET['keyword'] ?> where i want the "keyword" to show up?
sorry i don't know much about php