MySQL: Return "0" even when data doesn't exist

Readme.MD

What is happening:

DATE	COUNTER
2012-01-01	32
2012-01-02	28
2012-01-04	12
2012-01-05	23

As you can see, on 2012-01-03 dates there isn't any data. So the goal is to create a query (without procedure) to produce below result:

DATE	COUNTER
2012-01-01	32
2012-01-02	28
2012-01-03	1
2012-01-04	12
2012-01-05	23

query.sql

SELECT
  a.join_date, IFNULL(b.total, 0) theCount
FROM 
	(SELECT @curDate := Date_Add(@curDate, interval 1 day) AS join_date
    FROM (SELECT @curDate := Date_Add('2012-01-01', interval -1 day) ) sqlvars, users LIMIT 5 
  ) 
  a
LEFT JOIN (
	SELECT DATE_FORMAT(FROM_UNIXTIME(created_on), '%Y-%m-%d') AS tanggal, count(*) AS total
	FROM users u
  WHERE u.active = 1
  GROUP BY tanggal
) b on b.tanggal = a.join_date
ORDER BY a.join_date ASC