order by where in in laravel with requests

I want to make products to be ordered according to each user request as code below and here is the code

$pagination = Session::get('page');
if(Session::get('page') == NULL){
    Session::put('page',12);
}
if($request->has('per_page')){
    Session::put('page',$request->per_page);
    $pagination = Session::get('page');
}
$pris = product_categories::where('category_id', $id)->pluck('product_id')->toArray();
$products = Product::whereIn('id' , $pris)->paginate($pagination);
$pagination = Session::get('page');
if($request->get('sort') == 'price_asc'){
    $products = $products->OrderBy('price','asc');
}elseif($request->get('sort') == 'price_desc'){
    $products = $products->OrderBy('price','desc');
}elseif($request->get('sort') == 'popular'){
    $products =   $products->OrderBy('views','desc');
}elseif($request->get('sort') == 'newest'){
    $products = $products->OrderBy('created_at','desc');
}

it return error orderby doesn’t exist on collection

Answer

Your orderBy() statements have to be added to the query before you run paginate:

$productsQuery = Product::whereIn('id' , $pris);
//$pagination = Session::get('page'); // not sure why this line is there?
if($request->get('sort') == 'price_asc'){
    $productsQuery ->OrderBy('price','asc');
}elseif($request->get('sort') == 'price_desc'){
    $productsQuery ->OrderBy('price','desc');
}elseif($request->get('sort') == 'popular'){
    $productsQuery ->OrderBy('views','desc');
}elseif($request->get('sort') == 'newest'){
    $productsQuery ->OrderBy('created_at','desc');
}
$products = $productsQuery->paginate($pagination);