upload_ci

public function attach_file() {
    $result = array('');
    if(!empty($_FILES['...'])) {

        $upload = $this->upload_data('log_spt_att_file', $upload_path, $filename);

        if(empty($upload['error'])){
            // insert db
        } else {
            // return error
            $result = $upload;
        }
    }

    echo json_encode($result);
}


public function upload_data($file_post, $upload_path, $filename, $allowed_types = NULL) {
    $config['upload_path'] = $upload_path;
    if(!file_exists($config['upload_path'])) {
        mkdir($config['upload_path']);
    }
    $config['allowed_types'] = 'xls|xlsx|csv|doc|docx|pdf|png|jpg|jpeg|ppt|pptx';
    $config['max_size'] = $this->config->item('max_upload');
    $config['overwrite'] = false;
    $config['file_name'] = $filename;

    if($allowed_types) {
        $config['allowed_types'] = $allowed_types;
    }

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

    if (!$this->upload->do_upload($file_post)) {
        $result['error'] = $this->upload->display_errors();
    } else {
        $result = $this->upload->data();
    }

    return $result;
}