[ОлегА]

<?php
$action =  ((isset($_GET['action']))   ?  $_GET['action']   : "");

function hello($member_id) {
     echo $member_id['name'];
}

switch($action) {
	case "t11":
	hello($member_id);
	break;
}
?>

или

<?php
$action =  ((isset($_GET['action']))   ?  $_GET['action']   : "");

function hello() {
     global $member_id;
     echo $member_id['name'];
}

switch($action) {
	case "t11":
	hello();
	break;
}
?>