Merge two stdClass object array in php - php

Question

I have the following two stdClass array from a loop. Now I need to merge them when when the key 'id' matches.
array (size=1)
0 =>
object(stdClass)[28]
public 'id' => string '78' (length=2)
public 'quantity' => string '5' (length=1)
array (size=1)
1 =>
object(stdClass)[31]
public 'product_id' => string '78' (length=2)
public 'quantity' => string '1' (length=1)
So the final array become
array (size=1)
1 =>
object(stdClass)[31]
public 'product_id' => string '78' (length=2)
public 'quantity' => string '6' (length=1)
Any help on how to do that ? I decode the original data using json_decode from [{"id":"78","quantity":"1"}] this format of data.

Answer 1

If you add an extra parameter to the json_decode, you can get the data as an associative array, which is much easier to work with. I've done a couple of versions ( the first is PHP 7 ), pick one which works with your system.
<?php
error_reporting ( E_ALL );
ini_set ( 'display_errors', 1 );
$arr1 = json_decode('[{"id":"78","quantity":"1"}, {"id":"79","quantity":"3"}]', true);
$arr2 = json_decode('[{"id":"78","quantity":"5"}]', true);
$arr3 = array_merge($arr1, $arr2);
// V7
$result = [];
foreach ( $arr3 as $element ) {
$result[$element['id']] = ($result[$element['id']]??0)
+ $element['quantity'];
}
print_r($result);
// Prior to V7
$result = array();
foreach ( $arr3 as $element ) {
if ( !isset($result[$element['id']]) ){
$result[$element['id']] = 0;
}
$result[$element['id']] += $element['quantity'];
}
print_r($result);
I've added another element to show how this adds up, but the output of this is...
Array
(
[78] => 6
[79] => 3
)
Array
(
[78] => 6
[79] => 3
)

Answer 2

Here is a solution that maintains the format in your original question.
It also uses array_reduce which is a concise way to process an array.
<?php
$input1 = '[{"id":"78","quantity":"7800"},
{"id":"79","quantity":"7900"},
{"id":"80","quantity":"8000"}]';
$input2 = '[{"id":"78","quantity":"6"},
{"id":"79","quantity":"8"},
{"id":"80","quantity":"6"},
{"id":"81","quantity":"7"}]';
$input1Arr = json_decode($input1);
$input2Arr = json_decode($input2);
$combinedArrays = array_merge($input1Arr, $input2Arr);
echo "combinedArrays = " . print_r($combinedArrays, true) . "\n";
$result = array_reduce($combinedArrays,
function($intermediateResult, $item){
if ( ! array_key_exists($item->id, $intermediateResult) ) {
// First time encountering an object with this id
$intermediateResult[$item->id] = $item;
}
else {
// We have an object with this id already so just add the quantity
$intermediateResult[$item->id]->quantity += $item->quantity;
}
return $intermediateResult;
}, []);
// Get the values from the result array
print_r(array_values($result));