mixing $_POST and $_GET vars

hi.. quick question.. a basic link <a ref ="foo.php?a=1">blah</a> allows you to process the vars in foo.php using $_GET, easy/basic enough. however, if i have a form from cat.php that does a 'post' of the form information/input to the foo.php, i'm then going to have to either change the form to do a 'get' or else i'm going to have to do both a $_GET, and a $_POST within foo.php to access the vars from the pages that are interfacing with foo.php. is there an easier/cleaner/better approach?? or do i really need/wind up doing something like if ($_GET['foo'])... if ($_POST['apple'])... and just have a mix of both methods within the code... thanks -bruce bedouglas@earthlink.net