PHP referencing variables in an array as foreach keys - php

Question

I know my title is quite ambivalent but if you bear me, you'll find it is not so bad :P
I have a class method that gets quite different database fields in any order and builds an array based on those fields (each key adds another level into the array).
Now, that's the easy part. I also have a correction function that unifies the e.g. costs by some demographic data. The problem is that I need to address the right level in the correction formula.
I try to make an example:
I ask fields A,year,B,C,D and my correction formula for D depends on the year and C. I have formalized so that C and D are always the last ones to list but the problem is that how do I address the year so that I could get out an answer like [A][year][B]=function(year,c,d). The fields are in an array ($retr['fields']=array("A","year","B","C") (the result D comes automatically)
I tried to use foreach like
$retr['fields']=array("A","year","B","C")
$temp=get_data($retr);
foreach($temp as $${$retr['fields'][0]} => $yd)
foreach ($yd as $${$retr['fields'][1]} => $cd) {
$output[$${$retr['fields'][0]}][$${$retr['fields'][1]}]=0;
foreach ($cd as $a => $v)
$output[$${$retr['fields'][0]}][$${$retr['fields'][1]}]+=$v*$act[$year][$a]
and so on, but it seems that one can't use a variable variable as a key in foreach (or then I have got the syntax wrong). As now it just says that "Undefined variable: year"
Do you have any ideas how to express what I need?

Answer 1

Well I solved it, or rather not solved but programmed around.
For each foreach I checked the corresponding field and if it was year, I made a variable with value of current foreach key and referenced it with $$variable.
Like this:
$temp=get_data($retr);
foreach($temp as $varA => $yd) {
if ($retr[0]=="year")
$year_var=varA;
.
.
.
$output[$varA][$varB]+=$v*$act[$$year_var][$a]
I still would have preferred a cleaner solution but given my timeframe (or rather the loss of it) this should suffice.
I'm still interested in the "perfect solution"(TM)
Thx anyway :)

Answer 2

It's kind of hard to understand your structure, but it appears you're fetching some data items and then categorize them into tree-like structure.
In this case, even though a particular attribute (e.g. year) appears on some upper level it's still, essentially, an attribute of the data item itself, so keep it as such: convert the "value" into a non-scalar (either object or hash). Then you would be able to work with those attributes without referencing outer loop values (and without resorting to variable variables):
foreach($arr as $subarr) {
foreach ($subarr as $subsubarr) {
// ... and so on
foreach ($lastlevel as $value) {
$adjusted = correctionFunc($value->data, $value->year, $value->somethingelse); // assuming value is an object
}
}
}