How to upload multiple images using codeigniter?

I'm trying to upload multiple image using codeigniter thats actually working fine, But I want to store images to specific directory. My directory structure is

uploads/real/

inside this directory I want to create one more directory with the name of userid so directory structure becomes

uplods/real/20

I added logic and written some code like below: Consider $path="real", and $userid="20"

function image_upload($path,$userid)
    {
        $basepath = "uploads/".$path;
        echo "base-path > ".$basepath;
        echo "<br>working-dir > ".getcwd();
        chdir($basepath);
        echo "<br>working-dir > ".getcwd();
        if(!file_exists($userid)){
            mkdir($userid);
            chdir($userid);
            echo "<br>Working-dir > ".getcwd();
            $filesCount = count($_FILES['image']['name']);
            echo "<br> FileCount > ".$filesCount;
            for($i = 0; $i < $filesCount; $i++){
                $_FILES['img']['name'] = $_FILES['image']['name'][$i];
                $_FILES['img']['type'] = $_FILES['image']['type'][$i];
                $_FILES['img']['tmp_name'] = $_FILES['image']['tmp_name'][$i];
                $_FILES['img']['error'] = $_FILES['image']['error'][$i];
                $_FILES['img']['size'] = $_FILES['image']['size'][$i];

                echo "<br>FILES-Array > <pre>";
                print_r($_FILES);
                echo "<pre>";

                $config['upload_path']= "/";
                $config['file_name']=$userid .$i. '.jpg';
                $config['allowed_types']= 'jpg|png';
                $config['max_size']= 2048;

                echo "<br>CONFIG-Array > <pre>";
                print_r($config);
                echo "<pre>";

                $this->load->library('upload', $config);
                $this->upload->initialize($config);

                if ( ! $this->upload->do_upload('img'))
                {
                    $error = array('error' => $this->upload->display_errors());
                    echo "<br>UPLOAD-ERROR > <pre>";
                    print_r($error);
                    echo "<pre>";
                }
                else
                {
                    $da = array('upload_data' => $this->upload->data());
                    echo "_________IMAGE UPLOADED_______";
                }
            }

        }else{
            echo "<br>Folder Exist ...";
        }
        die();

And Browser Output is :

base-path > uploads/real
working-dir > C:\wamp64\www\ob_03
working-dir > C:\wamp64\www\ob_03\uploads\real
Working-dir > C:\wamp64\www\ob_03\uploads\real\20
FileCount > 1
    FILES-Array >
Array
(
    [image] => Array
        (
            [name] => Array
                (
                    [0] => abhi.jpg
                )

            [type] => Array
                (
                    [0] => image/jpeg
                )

            [tmp_name] => Array
                (
                    [0] => C:\wamp64\tmp\php336F.tmp
                )

            [error] => Array
                (
                    [0] => 0
                )

            [size] => Array
                (
                    [0] => 72125
                )

        )

    [img] => Array
        (
            [name] => abhi.jpg
            [type] => image/jpeg
            [tmp_name] => C:\wamp64\tmp\php336F.tmp
            [error] => 0
            [size] => 72125
        )

)
CONFIG-Array > 
Array
(
    [upload_path] => /
    [file_name] => 180.jpg
    [allowed_types] => jpg|png
    [max_size] => 2048
)
_________IMAGE UPLOADED_______

I'm not getting any error on printing print_r($error); But image is not uploaded to my directory WHY?