Autovivification in PHP - php

Question

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
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

Answer 1

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).

Answer 2

$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);