get the sum and difference of two associate array in php - php

Question

I have 2 arrays.
arr1 =array('cat'=>5,'dog'=>2);
arr2 = array('cat'=>1,'dog'=>2);
I need to get the sum of 2 arrays and the difference of these arrays.
arr3 = array(cat =>6,dog =>4);
arr4 = array(cat =>4 ,dog =>0);
I tried USING array_merge,array_diff,array_combine
But nothing gives me what i need.
plz help

Answer 1

Assuming we have the same number of like keys in both arrays we can iterate through one or the other and find and work with the corresponding values belonging to the other identified by the same named keys.
<?php
$a1 = array('cat'=>5,'dog'=>2);
$a2 = array('cat'=>1,'dog'=>2);
foreach($a1 as $k => $v)
{
$add[$k] = $v + $a2[$k];
$sub[$k] = $v - $a2[$k];
}
var_dump($add, $sub);
Output:
array(2) {
["cat"]=>
int(6)
["dog"]=>
int(4)
}
array(2) {
["cat"]=>
int(4)
["dog"]=>
int(0)
}

Answer 2

You could always resolve the first problem with array_sum.
Second is more interesting, I'd solve it with an array_map. See it in action here
$subtracted = array_map(function ($x, $y) {
return $x - $y;
}, $arr1, $arr2);
$result = array_combine(array_keys($arr1), $subtracted);
Note that you can also solve the first problem by replacing - with + in the above example.
Also note that array_map tends to be generally more readable.

Answer 3

Simple foreach can do it, below example if some key is missing and just getting difference not in -ve Negative sign, the difference would be 4 not -4 for 1 cat - 5 cat
<?php
$arr1 =array('cat'=>5,'dog'=>2);
$arr2 = array('cat'=>1,'dog'=>2);
$sum= [];
$sub= [];
foreach(array_merge($arr1,$arr2) as $k=>$v){
$a1 = $arr1[$k] ?? 0;
$a2 = $arr2[$k] ?? 0;
$sum[$k] = $a1 + $a2;
$sub[$k] = abs($a1 - $a2);
}
print_r($sum);
print_r($sub);
?>
Live Demo
With simple foreach loop
If some data exist only in single array