Unrest value in a 'foreach' loop - php

Question

I have an order like this
product quantity inventory
1 5 50
1 6 50
7 2 150
1 6 50
I am trying to loop in each product and decrease the inventory
Total inventory for product 1 is 50
in loop
product 1 the inventory become 45
product 1 the inventory becomes 39
product 7 the inventory becomes 148
product 1 the inventory becomes 44
Hers is the issue in the last loop the inventory has been rest to 50 again.
here is my code
foreach($order->productId->inventory as $currentRequestedCount){
$currentRequested = $order->quantity * $order->relatedPackage ->unit_count;
if($currentRequestedCount->type == "existing"){
$currentRequested -= $currentRequestedCount->amount;
}
}
how to prevent the $currentRequestedCount from being reset?

Answer 1

I use arrays to illustrate this. You have your inventory:
$inventory = [
//product => inventory
1 => 50,
7 => 150,
];
You get a few orders:
$order = [
['product' => 1, 'quantity' => 5],
['product' => 1, 'quantity' => 6],
['product' => 7, 'quantity' => 2],
['product' => 1, 'quantity' => 6],
];
The orders are processed (without handling errors!).
foreach($order as $row){
$inventory[$row['product']] -= $row['quantity'];
}
The current inventory:
var_dump($inventory);
Output:
array(2) {
[1]=>
int(33)
[7]=>
int(148)
}