This is either a mess up in the code, or you are trying to make the variable have different values. The reaon I say this is the . after the =
$whatever=.$_GET["whatever"];
If you want it to be just one variable to have one value, do it like this.
$whatever = $_GET["whatever"];
Then you have to make sure that the whatever variable is set in the url that it is calling from.
EXAMPLE:
http://www.whatever.com/hi.php?whatever=something
Then, the above url will give $whatever, the value of something.
Hope that helps,
-Blake