help with a join query

Here's the query what's causing me some trouble.

SELECT ar.ID as aID, ar.username as auser, ar.refID, m.user_id,m.username as muser
FROM ag_refered ar
LEFT JOIN members m ON ('m.user_id' = 'ar.refID')

Ive checked the database and in ag_refered there is a record with the values
ID = 1
username = SomeUser
refID = 96

and in the members table i have a record
user_id = 96
username = testRefer

yet when i run the query in something like PHPMyAdmin i get this

aID | auser | refID | user_id | muser
1 | SomeUser | 96 | NULL | NULL



Can anyone see why?

EDIT: Both tables are in the same database and the correct database is defined in my connection. If also tried the ON ('m.user_id' = 'ar.refID') like ON ('ar.refID' = 'm.user_id') too and i get the same reuslt

Because as far as mySQL is concerned, you're joining where two (different) strings are the same. By putting it in quotes, its interpreting m.user_ID and ar.refID as strings, so...

SELECT ar.ID as aID, ar.username as auser, ar.refID, m.user_id,m.username as muser
FROM ag_refered ar
LEFT JOIN members m ON m.user_id = ar.refID