any danger in overwriting $_GET ?

Hi, Is there any danger in overwriting the $_GET array? Will it still remain a superglobal in all circumstances? <? // Example 1: $_GET['foo'] = base64_decode($_GET['foo']); // modify a value // Example 2: $_GET = array(); // empty it $_GET['myNewKey'] = 'something'; // re-populate ?> I'm considering the "search engine friendly URL" methods discussed many times here and all over the web, but want to: a) maintain using $_GET, to ensure speedy conversion of old scripts b) maintain a certain level of familiarity in the way I (and others) write scripts c) have the values as superglobals (ie, available within functions) TIA Justin French