$productid = 'abc'; //sample product id
for($i = 0; $i < $perPage; $i++){
  $product = Product::where("product-new", $productid)->get()->toArray();
  if($product){
     $result[] = $product[0];
     $productid = $product[0]['product-old']; //xyz
  }

$productid = 'abc'; //sample product id
for($i = 0; $i < $perPage; $i++){
  $product = Product::where("product-new", $productid)->get()->toArray();
  if($product){
     $result[] = $product[0];
     $productid = $product[0]['product-old']; //xyz
  }

if ($product){
     $result[] = $product[0];
     $productid = $product[0]['product-old']; //xyz
 } else {
     break;
 }