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.

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 unless setup_userdata is called.