exampel : isset function

error_reporting(E_ALL & ~E_NOTICE);
define(THIS_SCRIPT,'index.php');
define(INC,'./includes');
include_once('global.php');
include_once(INC."/class.block_control.php");

$area_r = $HTTP_SERVER_VARS['REQUEST_URI'] ;
setcookie ("area_re", $area_r,time()+360);
$block = new block_control('global');
$dir = '.';




$title = $setting['sitename'] ;
$do = $_GET['do'];

if(!isset($do)){
exit("you should be set var 'do' ");
}


//checking loop
if(!$userinfo['uid']) $do = 'notLogin';
elseif(!$userinfo['allow-add']) $do = 'NotAllow';
elseif(!$userinfo['email-active']){
header("Location: usercp?do=activeMail");
exit();
}elseif(!$userinfo['complete_profile']){
header("Location: usercp?do=complete");
exit();
}


switch($do){


case "NotAllow":
$left = $tpl->return_output('usercp/msg.tpl');
break;

case "complete":
$left = $tpl->return_output('usercp/msg-complete.tpl');
break;

case "activeMail":
$left = $tpl->return_output('usercp/msg-activeMail.tpl');
break;

}



$tpl->print_output('main.tpl');
$db->close();