The following scenario may be able to help you.
You have a file called index.php whereby the following HTML code is written inside:
<a href="test.php?parameter=1">click here to get the parameter</a>
On test.php you can do this:
echo "The parameter value is ";
echo $HTTP_GET_VARS["parameter"];
If you have register_globals turned on, just use $parameter to refer to the variable.