【新新手有关问题】cookie赋不了值

【新新手问题】cookie赋不了值
setcookie( "username ", "aaa ");    
setcookie( "userpass ", "bbb ");    
echo     $HTTP_COOKIE_VARS[ "username "];    
echo($userpass);    
echo($result[name]);    
 
 
上面语句只有echo($result[name]);能显示出内容echo     $HTTP_COOKIE_VARS[ "username "];和echo($userpass);都无法显示任何东西？请问哪里错了，谢谢！！！

------解决方案--------------------
$_COOKIE[ "username "];