1. Update ShopController to Handle Brand Filter

The `index` function in `ShopController.php` is modified to fetch all brands and apply a `WHERE IN` condition to the product query based on the comma-separated `brands` value from the query string.

Fetch Brands and Get Filter Parameter

public function index(Request $request)
{        
    // Existing sorting and size logic...
    $size = $request->query("size") ? $request->query("size") : 12; 
    $order = $request->query("orderby") ? $request->query("orderby") : 1; 
    // ... switch case logic for $o_column and $o_order ...
    
    // Fetch all brands to display on the sidebar
    $brands = Brand::orderBy("name","ASC")->get();
    
    // Get the brand filter parameter from the query string
    $f_brands = $request->query("brands"); // e.g., "1,5,10"
    // 1. Apply Brand Filter Condition
    $products = Product::where(function($query) use($f_brands) {
        // If brands are selected ($f_brands is not empty), filter by brand_id
        // Otherwise (orWhereRaw), if $f_brands is empty, the filter is effectively skipped,
        // allowing all products to be returned.
        $query->whereIn("brand_id", explode(",", $f_brands))
              ->orWhereRaw(""" . $f_brands . ""=""");
    })
    ->orderBy($o_column, $o_order)
    ->paginate($size);    
    
    // Return the brands and the active filter value to the view
    return view("shop", compact("products", "size", "order", "brands", "f_brands"));
} 

2. Update `shop.blade.php` for Brand Checkboxes

In `shop.blade.php`, the Brands section is updated to display a list of all brands retrieved from the controller. Checkboxes are added, and JavaScript is included to handle the selection and form submission.

Brand Filter HTML (Sidebar)

<div class="sidebar-widget">
    <h4 class="widget-title">Filter By Brands</h4>
    <div class="widget-checkbox widget-categories">
        <ul class="checkbox-items">
            @foreach ($brands as $brand)
                <li>
                    <input type="checkbox"
                        id="brand{{ $brand->id }}"
                        name="brands"
                        value="{{ $brand->id }}"
                        class="chk-brand"
                        {{-- Check if this brand'sID is in the comma-separated $f_brands string --}}
                        @if($f_brands && in_array($brand->id, explode(",", $f_brands))) checked="checked" @endif
                    >
                    <label for="brand{{ $brand->id }}">
                        <span></span>{{ $brand->name }}
                    </label>
                </li>
            @endforeach
        </ul>
    </div>
</div>

Hidden Input in Filter Form

A hidden input field is added to the main filtering form (`#frmfilter`) to store the comma-separated list of selected Brand IDs before submission.

<!-- Inside the main filtering form with id="frmfilter" -->
<input type="hidden" name="brands" id="hdnBrands" value="{{$f_brands}}">

JavaScript for Checkbox Logic

JavaScript is added to listen for changes on the brand checkboxes, compile the selected brand IDs into a comma-separated string, update the hidden field, and submit the form.

@push("scripts")
<script>
    // Event listener for Brand checkboxes
    $(".chk-brand").on("change", function() {
        var brands = "";
        
        // Loop through all checkboxes with class "chk-brand"
        $(".chk-brand").each(function() {
            if ($(this).is(":checked")) {
                // Compile selected brand IDs into a comma-separated string
                if (brands === "") {
                    brands += $(this).val();
                } else {
                    brands += "," + $(this).val();
                }
            }
        });
        // Set the value of the hidden input field
        $("#hdnBrands").val(brands);
        // Submit the form to apply the filter
        $("#frmfilter").submit();
    });
</script>
@endpush