Jesse's answer wasn't tested and will not provide the desired output because the "stocks" array wasn't being modified -- a copy of the array was being modified in the loop -- so if you try to print the result to screen, there would be no change.
To modify by reference, use &
just before the value variable in the first loop.
Also the unset()
key must come from the inner loop to be accurate.
Additionally, if the "sales" "product_id"s are unique, then breaking the inner loop upon matching will improve performance. (This is how array_search()
works.)
Code: (Demo)
$stocks = [
['product_id'=>2, 'stocks'=>50],
['product_id'=>3, 'stocks'=>100],
['product_id'=>4, 'stocks'=>20],
['product_id'=>5, 'stocks'=>60]
];
$sales = [
['product_id'=>4, 'quantity'=>3],
['product_id'=>5, 'quantity'=>30]
];
foreach ($stocks as &$row) { // modify by reference
foreach ($sales as $k => $row2) { // search for product_id match
if ($row['product_id'] == $row2['product_id']) {
$row['stocks'] -= $row2['quantity']; // subtract
unset($sales[$k]); // eliminate match from lookup array
break; // assuming $sales['product_id'] values are unique
}
}
}
var_export($stocks);
Output:
array (
0 =>
array (
'product_id' => 2,
'stocks' => 50,
),
1 =>
array (
'product_id' => 3,
'stocks' => 100,
),
2 =>
array (
'product_id' => 4,
'stocks' => 17,
),
3 =>
array (
'product_id' => 5,
'stocks' => 30,
),
)
Alternatively, you can converted the sales array into a flattened, product_id-keyed array to serve as a lookup.
Code: (Demo)
$keyed = array_column($sales, 'quantity', 'product_id');
var_export($keyed);
echo "\n---\n";
foreach ($stocks as &$row) { // modify by reference
if (isset($keyed[$row['product_id']])) { // search for product_id match
$row['stocks'] -= $keyed[$row['product_id']]; // subtract
}
}
var_export($stocks);
Output:
array (
4 => 3,
5 => 30,
)
---
array (
0 =>
array (
'product_id' => 2,
'stocks' => 50,
),
1 =>
array (
'product_id' => 3,
'stocks' => 100,
),
2 =>
array (
'product_id' => 4,
'stocks' => 17,
),
3 =>
array (
'product_id' => 5,
'stocks' => 30,
),
)