How to compare two associative arrays by key - php

Question

I am trying to compare two associative arrays and get the difference based upon the value and also based upon the key. I have tried using an array_filter with a closure
The two arrays are like so:
Array 1
$newArr = [
0 => [
'id' => 'UT5',
'qty' => '4'
],
1 => [
'id' => 'WRO',
'qty' => '3'
],
2 => [
'id' => 'SHO',
'qty' => '3'
]
];
Array 2
$oldArr = [
0 => [
'id' => 'SHO',
'qty' => '1'
],
1 => [
'id' => 'UT5',
'qty' => '2'
],
];
My desired output is as follows:
array(3)
{
["UT5"]=> int(2)
["SHO"]=> int(2)
["WRO"]=> int(3)
}
I have gotten this far:
<?php
$newArr = [
0 => [
'id' => 'UT5',
'qty' => '4'
],
1 => [
'id' => 'WRO',
'qty' => '3'
],
2 => [
'id' => 'SHO',
'qty' => '3'
]
];
$oldArr = [
0 => [
'id' => 'SHO',
'qty' => '1'
],
1 => [
'id' => 'UT5',
'qty' => '2'
],
];
$toAdd = [];
foreach ($newArr as $item) {
$itemsToAdd = array_walk($oldArr, function ($k) use ($item, &$toAdd) {
if ($k['id'] == $item['id']) {
$toAdd[$k['id']] = max($k['qty'], $item['qty']) - min($k['qty'], $item['qty']);
}
});
}
var_dump($toAdd); die();
However with this function, my current output is:
array(2) {
["UT5"]=> int(2)
["SHO"]=> int(2)
}
Note that WRO is missing. Is there a way that I can add a conditional to accurately check for this? I have tried a few solution such as !in_array and else but neither are giving me the desired output.
Any help is appreciated! Thanks!

Answer 1

That's an easy one, your code saves a value ONLY if the key is present in both arrays. Just add a clause to check if the key DOESN'T exist in the old array. (also do the opposite in case the old array has a key the new one doesn't have)
if (!isset(old array [ new array key ]){
$newArray[new array key] = new array key and values;
Your program structure is optimized for the computer and is too complex to follow as a human, I rewrote it entirely.
<?php
$newArr = [0 => ['id' => 'UT5', 'qty' => '4'], 1 => ['id' => 'WRO', 'qty' => '3'], 2 => ['id' => 'SHO', 'qty' => '3']];
$oldArr = [0 => ['id' => 'SHO', 'qty' => '1'], 1 => ['id' => 'UT5', 'qty' => '2'], ];
$newReset = [];
foreach( $newArr as $item ) {
$newReset[$item['id']] = $item['qty'];
}
$oldReset = [];
foreach( $oldArr as $item ) {
$oldReset[$item['id']] = $item['qty'];
}
foreach( $newReset as $key => $val ) {
if( isset( $oldReset[$key] ) ) {
$toAdd[$key] = max( $oldReset[$key], $val ) - min( $oldReset[$key], $val );
}
else $toAdd[$key] = intval($val);
}
var_dump( $toAdd );
And here's the result.
array(3) {
["UT5"]=>
int(2)
["WRO"]=>
int(3)
["SHO"]=>
int(2)
}

Answer 2

Make it in one pass
$toAdd = [];
foreach ($newArr as $item)
$toAdd[$item['id']] = $item['qty'];
foreach ($oldArr as $item)
if (isset($toAdd[$item['id']]))
$toAdd[$item['id']] = abs($toAdd[$item['id']] - $item['qty']);
else
$toAdd[$item['id']] = abs($item['qty']);
print_r($toAdd);