Upload de imagens gerando thumbnail, salvando no db

<?php

    function inserir(){


        $id_galeria = $this->input->post('id_galeria');

        $query = $this->db->query("SELECT * FROM galerias WHERE id='$id_galeria'");

        foreach($query->result() as $row){
            $pasta = $row->pasta;
        }

        $upload_conf = array(
            'upload_path' => realpath('uploads/galerias').'/'.$pasta.'/',
            'allowed_types' => 'gif|jpg|png|jpeg',
            'max_size' => '30000',
            'file_name' => md5(uniqid(time())) . ".jpg"
        );

        $this -> upload -> initialize($upload_conf);

        // Change $_FILES to new vars and loop them
        foreach ($_FILES['userfile'] as $key => $val) {
            $i = 1;
            foreach ($val as $v) {
                $field_name = "file_" . $i;
                $_FILES[$field_name][$key] = $v;
                $i++;
            }
        }

        // Unset the useless one ;)
        unset($_FILES['userfile']);

        // Put each errors and upload data to an array
        $error = array();
        $success = array();

        // main action to upload each file
        foreach ($_FILES as $field_name => $file) {

            if (!$this -> upload -> do_upload($field_name)) {
                // if upload fail, grab error
                //$error['upload'][] = $this -> upload -> display_errors();
                echo '<script>alert("Não foi possível cadastrar as imagens, tente mais tarde.");</script>';
                echo '<script>location.href="'.base_url('adm_galerias_fotos').'";</script>';
                return false;

            } else {
                // otherwise, put the upload datas here.
                // if you want to use database, put insert query in this loop
                $upload_data = $this -> upload -> data();

                // set the resize config
                $resize_conf = array(
                // it's something like "/full/path/to/the/image.jpg" maybe
                'source_image' => $upload_data['full_path'],
                // and it's "/full/path/to/the/" + "thumb_" + "image.jpg
                // or you can use 'create_thumbs' => true option instead
                //'new_image' => $upload_data['file_path'] . 'thumb_' . $upload_data['file_name'],
                'new_image' => $upload_data['file_path']. 'thumbs/' . $upload_data['file_name'],
                'width' => 300,
                'height' => 178);

                // initializing
                $this -> image_lib -> initialize($resize_conf);

                // do it!
                if (!$this -> image_lib -> resize()) {
                    // if got fail.
                    $error['resize'][] = $this -> image_lib -> display_errors();
                } else {
                    // otherwise, put each upload data to an array.
                    $success[] = $upload_data;
                }

                $img_db = $upload_data['file_name'];

                $_POST['foto'] = $img_db;

                $this->fotos_model->insert();

            }
        }

        // see what we get
        if (count($error > 0)) {
            $data['error'] = $error;
        } else {
            $data['success'] = $upload_data;
        }

        echo '<script>alert("Fotos cadastradas com sucesso");</script>';
    }