Image upload not working in codeignitor

I create image upload code. this create directory first and then upload images to it.

In form I upload 3 images.

My Code is:

$dir_path = 'assets/images/product_images/'.$model;
mkdir($dir_path, 0777);

$i = 1 ;

    foreach ($image as $new_image)
        {
            $dir_path_up = 'assets/images/product_images/'.$model."/";
            $filename = $_FILES["$new_image"]["name"];
            $image_name  = $dir_path_up .$filename . $i. ".jpg";
                echo $image_name;

                $i++;
        }
        die();

Result of echo

assets/images/product_images/255_2555/1.jpg
assets/images/product_images/255_2555/2.jpg
assets/images/product_images/255_2555/3.jpg

But that images are not getting uploade in to directory. I echo the image name which i created. Its alredy renamed. Then why images not getting uploade into directory.

what is wrong in this??