Stuck with union

I like to select 2 rows before and 2 rows after the selected row sorted by ID.

ID:1 - 2 - 3 - 4 - 5 - 6 - 8 - 9 - 10

Suppose $skip is 6, this is what I like to achieve:

4 - 5 - 7 - 8

My code:

(SELECT * FROM $table WHERE id < $skip ORDER BY id DESC LIMIT 2) union all (SELECT * FROM $table WHERE id > $skip ORDER BY id ASC LIMIT 2)

This is what I get:

5 - 4 - 7 - 8

This didn't fixed it:

((SELECT * FROM $table WHERE id < $skip ORDER BY id DESC LIMIT 2) ORDER BY id ASC) union all (SELECT * FROM $table WHERE id > $skip ORDER BY id ASC LIMIT 2)

Testing this sorts correct, so I think the problem must be union all?

SELECT * FROM $table WHERE id < $skip ORDER BY id DESC LIMIT 2

Any ideas how to fix the first part?

You have order by in the subqueries, but you should just add one to the outer query too:

(SELECT * FROM $table WHERE id < $skip ORDER BY id DESC LIMIT 2) 
UNION ALL 
(SELECT * FROM $table WHERE id > $skip ORDER BY id ASC LIMIT 2)
ORDER BY id;

Alternatively, you could use a window function (if you are on MySQL 8+):

WITH base AS (
  SELECT id, 
         LEAD(id) OVER (ORDER BY id) AS next_id,
         LEAD(id, 2) OVER (ORDER BY id) AS next2_id,
         LAG(id) OVER (ORDER BY id) AS prev_id,
         LAG(id, 2) OVER (ORDER BY id) AS prev2_id
  FROM $table
)
SELECT id FROM base WHERE $skip IN (next_id, next2_id, prev_id, prev2_id)
ORDER BY id;