CAN php script to hear, from what location variables are sent ??

i mean that i want to know , can the php script do next

  if(variables are setted in adressbar)
  {
    echo "error";
  } 
  else if(variables are setted in parent_script) 
  {
     all ok....
  }

You can specify different methods of variables by using the superglobal method like this:

if(isset($_POST[passedin])) {
.... the variable was send with the post method
}

other ones are:
$GET
$COOKIES
$SESSION
$REQUEST

is this what you are looking for ?