Is there a clean way to accomplish the following without writing an ugly bunch of for loops and logic blocks?
<?php
//INPUT
$aRaw = [
['in' => [1,2,3], 'out' =>[4,5,6]],
['in' => [7,8,9], 'out' =>[1,2,3]]
];
//DESIRED OUTPUT
$aSum = ['in' => [8,10,12], 'out' =>[5,7,9]];
?>
$aN is a factor, so there may only be one set in $aRaw or there may be 5+
Thank you =)
I mean, this works, but triple nested foreach loops makes my skin crawl AND throws undefined offsets where $sum is being filled:
<?php
//INPUT
$aRaw = [
['in' => [1,2,3], 'out' =>[4,5,6]],
['in' => [7,8,9], 'out' =>[1,2,3]]
];
$sum = [];
foreach($aRaw as $aSet) {
foreach($aSet as $k => $kv) {
$i = 0;
foreach($kv as $v) {
$sum[$k][$i] += $v;
$i++;
}
}
}
print_r($sum);
?>
Array
(
[in] => Array
(
[0] => 8
[1] => 10
[2] => 12
)
[out] => Array
(
[0] => 5
[1] => 7
[2] => 9
)
)
Gotta be a better way
So far everything else I think of ends up more complicated. 
Change:
// from this
$sum = [];
// to this
$sum = [array_fill(0,3,0), array_fill(0,3,0)];
And that will remove the notices from it being undefined. Everything is going to involve nested loops unfortunately, even if you us array_map and friends, you're just moving the loop to inside the C function.
Thanks guys... Added in @'s suggestion and it's workin'
Was hoping for a more elegant way but needs vs wants