Upload File Codeigniter

$file_name = $_FILES['files']['name'];
		$config['upload_path'] ='img/';
		$config['allowed_types'] = 'gif|jpg|png|mp3|pdf|rar|zip';
		$config['max_size']	= '0';
		$config['max_width']  = '0';
		$config['max_height']  = '0';
		$config['overwrite'] = true;
		$config['file_name'] = $file_name;
		$this->load->library('upload',$config);

		if (!$this->upload->do_upload('files'))
		{
			$errors = $this->upload->display_errors();
			var_dump($errors);
		}
		else
		{

			echo json_encode(array('message' => $file_name, 'as'=>'as'));
		}