Q:

Select all Filters from Products which belongs to one Category in Laravel

I have these tables:

Category
Line
Product
Filter
Product_filter

Category -> Line -> Product -> Filter
One product has many filters
One product has one category and one line
I need to get all the filters for one category.
Today, through relationships between the tables, I can get all the products from on category and all the filters from one product:
// All the products
$category->products

// All the filters
$product->filters

//or
$category->products->first()->filters

Now, I need to get the filters by category, something like:
$category->filters
// or
$category->products->filters

A small brief:

A category has products who have filters

How to get all the filters by Category?

A:

In your Category model:
public function filters()
{
    return Filter

        ::join('filter_product', 'filter.id', '=', 'filter_product.filter_id')

        ->join('products', 'filter_product.product_id', '=', 'products.id')

        ->join('categories', 'products.category_id', '=', 'categories.id')

        ->where('categories.id', $this->id);
}

public function getFiltersAttribute()
{
    if (!$this->relationLoaded('products') || 
        !$this->products->first()->relationLoaded('filters')) {
        $this->load('products.filters');
    }

    return collect($this->products->lists('filters'))->collapse()->unique();
}

Then you will be able to use it like this:
$category->filters

To guarantee unique filter results, you need to pass the unique fields, for ex. id: 
return collect($this->products->lists('filters'))->collapse()->unique('id');

