Don't you hate it when you forget to "global $wpdb;"? Here is a solution:
<?php
$a = 'Andy';
function g() {
return 'foreach(array_keys($GLOBALS) as $g)global $$g;unset($g);';
}
function go() {
eval(g());
var_dump($a);
}
go();
?>
Andy
(Sorry, couldn't wait for April.)