Script upload multiple file in CodeIgniter

multiplefile.php

<?php 

if ($_FILES AND $_FILES['surat_file']['name']) {
            $count_file = count($_FILES['surat_files']['name']);
            for ($i = 0; $i < $count_file; $i++) {
                $_FILES['surat_file']['name'] = $_FILES['surat_files']['name'][$i];
                $_FILES['surat_file']['type'] = $_FILES['surat_files']['type'][$i];
                $_FILES['surat_file']['tmp_name'] = $_FILES['surat_files']['tmp_name'][$i];
                $_FILES['surat_file']['error'] = $_FILES['surat_files']['error'][$i];
                $_FILES['surat_file']['size'] = $_FILES['surat_files']['size'][$i];

                $config = array(
                    'upload_path' => 'uploads/surat-masuk/',
                    'allowed_types' => 'jpeg|jpg|png|pdf',
                );
    
                $this->load->library('upload', $config);
                $this->upload->initialize($config);
                if ($this->upload->do_upload('surat_file')) {
                    $file = $this->upload->data();
                    $lampiran[$i]['surat_id'] = $surat_id;
                    $lampiran[$i]['lampiran_path'] = $config['upload_path'].$file['file_name'];
                    $lampiran[$i]['nama'] = $file['file_name'];
                    $lampiran[$i]['size'] = $file['file_size'];
                    $lampiran[$i]['tipe'] = $file['file_ext'];
                    $lampiran[$i]['created_by'] = $user->id_user;
                    $lampiran[$i]['created_at'] = date("Y-m-d H:i:s", time());
                    $lampiran[$i]['unit_author'] = $user->unit_kerja;
                    $lampiran[$i]['sunit_author'] = $user->sunit_kerja;
                }
            }   
        }
?>