Get all product related to category ids

This part is calling a function (most likely a query builder)

 $category->products();

//Should be
 $category->products;

Also, I hope that you preload your relations? If not this will give you alot of database queries.

my bad i did not see the function :'(

So if i have multiple product categories and with multiple collection how i can merge all and give a single array or collection do view for example

I have the two categories and it will give me correct results like belwo

array:2 [▼
  0 => Collection {#328 ▼
    #items: array:5 [▶]
  }
  1 => Collection {#341 ▼
    #items: array:1 [▶]
  }
]

so how i can can make a single 5+1 array and pass to view ?

If you need to do it like that, this should work (if I knew more about you actual data, it could probably be done much simpler, by simply getting all product category Ids, and then running a whereIn on Product::

$productsOfThisCategory = collect([]);
        foreach($ProductCategories as $category) {
            $productsOfThisCategory->merge($category->products);
        }

i try the above but it gives me

Collection {#315 ▼
  #items: []
}

Oh sorry forgot that it does not mutate

$productsOfThisCategory = collect([]);
        foreach($ProductCategories as $category) {
            $productsOfThisCategory = $productsOfThisCategory->merge($category->products);
        }

Yes this works Great. Any idea how to exclude the item which repeat again i mean every category ?

try using unique

$productsOfThisCategory = $productsOfThisCategory->unique('id')->values()->all();