clarification on GROUP_CONCAT()

[newbie93]

Hi everyone - I need a way to turn a column in my table into a list. Basically, my table consists of: userId, name, and "role" (0 or 1). I want to write a function that outputs a list of usernames. This is what I have:

 
         function checking_query() {
        global $connection;
        $query = "SELECT GROUP_CONCAT(userId) FROM owner";
        $result = mysql_query($query, $connection);
        confirm_query($result);
        var_dump($result);
    }
 

I get no result when I do this (nor do I get an error message...)
Please help! I feel terrible wasting so much time on this issue because I have a feeling it's pretty trivial

[Luuk]

mysql> select * from tbl2;
+----------+----------+----------+
| colA     | colB     | colC     |
+----------+----------+----------+
| 33996344 | 33996351 | 33996344 |
| 50331648 | 68257567 | 50331648 |
| 67276832 | 68257567 | 67276832 |
+----------+----------+----------+
3 rows in set (0.00 sec)
 
mysql> select group_concat(colA) from tbl2;
+----------------------------+
| group_concat(colA)         |
+----------------------------+
| 33996344,50331648,67276832 |
+----------------------------+
1 row in set (0.00 sec)
 

With above, i can say that there is nothing wrong with your query but:
1) does "select * from owner" return results?
2) what does "confirm_query($result);" do?