PHP JSON parsing returns duplicate objects

Somehow the following php code returns 2 JSONs objects instead of 1 object. anyone can see the reason?

the output present the same row duplicated: - first: all the row values - second: (that I need), all the row values + extra sql values

note: already tried mysql_fetch_assoc, it return only the row values

$query = "
select u.*,
            COALESCE((SELECT count(t.production)
                FROM Transcriptions t
                where t.ACCOUNT_ID = u.ACCOUNT_ID
                and t.production = 1
                group by u.ACCOUNT_ID
           ),0) as transcriptions_count
from users u";  


$result = mysql_query($query, $connection);    

while ($row = mysql_fetch_array($result))
        {        
             $objects[] = $row;
        }
echo json_encode($objects);

output:

[{"0":"10463","PID":"10463"},{"PID":"10463","transcriptions_count":"158"}]

output should return:

[{"PID":"10463","transcriptions_count":"158"}]