Collection operations

Hello! Can you please help me with the following situation.

I have a collection of orders. I also have a "hasMany" relationship with an items table that contains basically the lines of the order (products). I want to find out how many pieces of each product I need in order to satisfy the necessity of those orders.

What can't be seen in the item collection is a product_id field and also the product_quantity filed.

Practically, out of this I would like to get the total number of products I need, in order for all of those orders to be fulfilled.

Collection {#488 ▼ #items: array:23 [▼ 0 => Order {#417 ▶} 1 => Order {#418 ▼ #table: "bdm_orders" #primaryKey: "order_id" +timestamps: false #connection: null #keyType: "int" #perPage: 15 +incrementing: true #attributes: array:23 [▶] #original: array:23 [▶] #relations: array:1 [▼ "items" => Collection {#416 ▼ #items: array:2 [▼ 0 => OrderItem {#490 ▼ #table: "bdm_order_item" #primaryKey: "order_item_id" +timestamps: false #connection: null #keyType: "int" #perPage: 15 +incrementing: true #attributes: array:7 [ …7] #original: array:7 [ …7] #relations: [] #hidden: [] #visible: [] #appends: [] #fillable: [] #guarded: array:1 [ …1] #dates: [] #dateFormat: null #casts: [] #touches: [] #observables: [] #with: [] #morphClass: null +exists: true +wasRecentlyCreated: false } 1 => OrderItem {#491 ▶} ] } ] #hidden: [] #visible: [] #appends: [] #fillable: [] #guarded: array:1 [▶] #dates: [] #dateFormat: null #casts: [] #touches: [] #observables: [] #with: [] #morphClass: null +exists: true +wasRecentlyCreated: false } 2 => Order {#419 ▶} 3 => Order {#420 ▶} 4 => Order {#421 ▶} 5 => Order {#422 ▶} 6 => Order {#423 ▶} 7 => Order {#424 ▶} 8 => Order {#425 ▶} 9 => Order {#426 ▶} 10 => Order {#427 ▶} 11 => Order {#428 ▶} 12 => Order {#429 ▶} 13 => Order {#430 ▶} 14 => Order {#431 ▶} 15 => Order {#432 ▶} 16 => Order {#433 ▶} 17 => Order {#434 ▶} 18 => Order {#435 ▶} 19 => Order {#436 ▶} 20 => Order {#437 ▶} 21 => Order {#438 ▶} 22 => Order {#439 ▶} ] }

Thank you!