小编Sac*_*dav的帖子

我有这个代码。

$message = "";

if($_REQUEST['msg'] == "new"){
    $message = "New User has been added successfully";
}else if($_REQUEST['msg'] == 'edit'){
    $message = "User has been saved successfully";
}else if($_REQUEST['msg'] == 'update'){
    $message = "User(s) has been Updated successfully";
}

有人可以在这里告诉我[[msg]]是什么，并请说明$ _REQUEST的功能吗？