> I got the undefined variable : user_id when i use get_user_meta

This is because `$user_id` is empty and undefined, you need to give it a value, and that value needs to be the ID of a user.

> when i try put the above code below this line

> no error occur but my value $phone and $icno become empty


Yes, you gave `$user_id` a value so it worked. The reason phone and icno are empty is because there is no user meta for phone and icno. **The order you do things in matters.** Code is executed from the top of the file to the bottom.

You can't retrieve values before they are added, and you can't use variables before they are set.

2 final notes:

 - indenting your code is important, especially if you share it with other people, and it eliminates an entire class of bugs
 - `global $wpdb, $user_ID;` should be removed. The code never uses `$wpdb` and there is no `$user_ID` global variable.