从Codeigniter中的http post请求获取附件

I'm using Mailgun to receive emails for my web app developed using Codeigniter. Mailgun makes a http post to the following (http://something.com/email) url for every incoming email.

I get the contents of the email with the following code.

function email_to_db(){
   $email_body = $this->input->post('body-plain', '');
   $email_sender = $this->input->post('sender');
}

However I'm not able to fetch the attachments.
Can someone guide me on how I can achieve this. Following is the link to my reference doc.

attachments are files, you should use File Uploading Class

$config = [];
$config['upload_path']          = './uploads/';
$config['allowed_types']        = 'gif|jpg|png';
$config['max_size']             = 100;
$config['max_width']            = 1024;
$config['max_height']           = 768;

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

if (!$this->upload->do_upload())
{
    $error = array('error' => $this->upload->display_errors());
}
else
{
    $data = array('upload_data' => $this->upload->data());
}

you can also do print_r($_FILES); and check the attachment files.