How to merge two arrays diferents on one - php

Question

How to update an array of objects, adding the quantities if you already have the same ID, or if you have not created a new object.
I tried to explain in the code with the arrays and also with the idea of how I would like the result to be.
old Array
$a1 = [
array(
"id" => 1,
"qty" => 1
),
array(
"id" => 2,
"qty" => 1
)
];
$a2 = [
array(
"id" => 1,
"qty" => 1
)
];
$output = array_merge($a1, $a2);
echo '<pre>';
print_r($output);
echo '</pre>';
Result Error:
Array
(
[0] => Array
(
[id] => 1
[qty] => 1
)
[1] => Array
(
[id] => 2
[qty] => 1
)
[2] => Array
(
[id] => 1
[qty] => 1
)
)
What I need, in addition to if the ID does not contain, add.
Array
(
[0] => Array
(
[id] => 1
[qty] => 2
)
[1] => Array
(
[id] => 2
[qty] => 1
)
)

Answer 1

You can take the first array as base, then search for the key (if existing) where the product matches the id. Then either add the quantity and recalculate the price or you just add the reformatted element (id to product conversion).
$result = $a;
foreach($b as $element) {
$matchingProductIndex = array_search($element['id'], array_column($a, 'product'));
if ($matchingProductIndex !== false) {
$pricePerUnit = $result[$matchingProductIndex]['price'] / $result[$matchingProductIndex]['qty'];
$result[$matchingProductIndex]['qty'] += $element['qty'];
$result[$matchingProductIndex]['price'] = $result[$matchingProductIndex]['qty'] * $pricePerUnit;
} else {
$result[] = [
'qty' => $element['qty'],
'product' => $element['id'],
'price' => $element['price'],
];
}
}
print_r($result);
Working example.

Answer 2

Loop through both arrays with foreach and check the ids against each other.
https://paiza.io/projects/lnnl5HeJSFIOz_6KD6HRIw
<?php
$arr1 = [['qty' => 4, 'id' => 4],['qty' => 1,'id' => 30]];
$arr2 = [['id' => 30, 'qty' => 19],['id' => 31, 'qty' => 2]];
$arr3 = [];
foreach($arr1 as $iArr1){
$match = false;
foreach($arr2 as $iArr2){
if($iArr1['id'] === $iArr2['id']){
$arr3[] = ['id' => $iArr1['id'], 'qty' => $iArr1['qty'] + $iArr2['qty']];
$match = true;
}
}
if(!$match){
$arr3[] = $iArr1;
$arr3[] = $iArr2;
}
}
print_r($arr3);
?>

Answer 3

One approach could be one I more often suggested.
First lets merge $a2 with one to simplify looping over one larger collection.
If we then create a small mapping from id to its index in the result array we can update the running total of qty.
$map = [];
$result = [];
// Merge the two and do as per usual, create a mapping
// from id to index and update the qty at the corresponding index.
foreach (array_merge($a1, $a2) as $subarr) {
$id = $subarr['id'];
if (!key_exists($id, $map)) {
$index = array_push($result, $subarr) - 1;
$map[$id] = $index;
continue;
}
$result[$map[$id]]['qty'] += $subarr['qty'];
}
echo '<pre>', print_r($result, true), '</pre>';
Output:
Array
(
[0] => Array
(
[id] => 1
[qty] => 2
)
[1] => Array
(
[id] => 2
[qty] => 1
)
)