Autovivification in PHP

if I have this SQL query:

select substring(id for 2) as key, 
yw, count(*)
from pref_money group by yw, key

returning number of users per week and per key:

 key |   yw    | count
-----+---------+-------
 VK  | 2010-45 |   144
 VK  | 2010-44 |    79
 MR  | 2010-46 |    72
 OK  | 2010-48 |   415
 FB  | 2010-45 |    11开发者_Go百科
 FB  | 2010-44 |     8
 MR  | 2010-47 |    55
 VK  | 2010-47 |   136
 DE  | 2010-48 |    35
 VK  | 2010-46 |   124
 MR  | 2010-44 |    40
 MR  | 2010-45 |    58
 FB  | 2010-47 |    13
 FB  | 2010-46 |    13
 OK  | 2010-47 |  1834
 MR  | 2010-48 |    13
 OK  | 2010-46 |  1787
 DE  | 2010-44 |    83
 DE  | 2010-45 |   128
 FB  | 2010-48 |     4
 OK  | 2010-44 |  1099
 OK  | 2010-45 |  1684
 DE  | 2010-46 |   118
 VK  | 2010-48 |    29
 DE  | 2010-47 |   148

Then how can I please count those users? I'm trying:

    $sth = $db->prepare('select substring(id for 2) as key, yw, count(*)
                         from pref_money group by yw, key');
    $sth->execute();
    while ($row = $sth->fetch(PDO::FETCH_ASSOC))
            ++$users[$row['yw']][$row['key']];
    print_r($users);

but get numerous errors.

I'm trying to get the data for a stacked bars diagram. The x-axis will show the week numbers and the y-axis will show number of users, grouped by the key strings.

Thank you! Alex

Are you trying to total the count column or just get number of rows returned? If the latter, php has a method for that. if the former, you need to make it $users[$row['yw']][$row['key'] += $row['count'] instead (assuming the array has already been created).

$sth = $db->prepare('select substring(id for 2) as key, yw, count(*)
                         from pref_money group by yw, key');
    $sth->execute();
    $users=array();  //  register $users as an array.
    while ($row = $sth->fetch(PDO::FETCH_ASSOC))
            if(!isset($users[$row['yw']])){// see if $users['whatever_key'] has already been set
               $users[$row['yw']]=0;//if not, initialize it as a default starting value of 0
             }
            $users[$row['yw']]+=$row['key'];//now we won't get any nasty notices here about undeclared variables or keys..
    print_r($users);