function get_target_file() {
$userfile = array_keys($_FILES)[0];
return $userfile;
}

private function validate_file($key, $label, $rules) {

require_once('file_validation_helper.php');

}

<?php
class Pic extends Trongate {

function index() {
$data['filebank'] = 'filebank';
$data['fileexperience'] = 'fileexperience';
$data['filephotopassport'] = 'filephotopassport';
$data['fileaddress'] = 'fileaddress';

$data['view_module'] = 'pic';
$this->view('display', $data);
}

function submit_upload_picture($update_id) {

$this->module('trongate_security');
$this->trongate_security->_make_sure_allowed();

$submit = post('submit');

if ($submit == 'Upload') {

// create image directory using id as name, in current module/assets or public folder
$picture_settings = $this->_init_picture_settings();
$this->_make_sure_got_destination_folders($update_id, $picture_settings);
extract($picture_settings);

$files = $_FILES; // make copy

foreach ($_FILES as $key => $value) {

if ($value['error'] == 0) {
// custom validate user file
if ($this->custom_validate($key, $max_file_size)) {

// picture selected
$config['destination'] = $destination . '/' . $update_id;
$config['max_width'] = $resized_max_width;
$config['max_height'] = $resized_max_height;

if ($thumbnail_dir !== '') {
$config['thumbnail_dir'] = $thumbnail_dir . '/' . $update_id;
$config['thumbnail_max_width'] = $thumbnail_max_width;
$config['thumbnail_max_height'] = $thumbnail_max_height;
}

//upload the picture
$config['upload_to_module'] = (!isset($picture_settings['upload_to_module']) ? false : $picture_settings['upload_to_module']);
$this->upload_picture($config); // upload single image
} else {
redirect($_SERVER['HTTP_REFERER']);
}

//update the database with the file name or clear it if none uploaded
$data[$key] = $value['name'];
$this->model->update($update_id, $data, 'freizas');

$flash_msg = 'The pictures were successfully uploaded';
}
unset($_FILES[$key]); // remove current userfile object
}
// restore $_Files array object or delete this if you don't want it anymore
$_FILES = $files;

set_flashdata($flash_msg);
redirect($_SERVER['HTTP_REFERER']);
}
}

function custom_validate($key, $max_size) {
$error_msg = [];
$target_file = $_FILES[$key];
$temp_file_name = $target_file['tmp_name'];
//$file_size = $target_file['size'] / 1000; //kilobytes)

// check allowed types
$allowed_types = ['gif', 'jpg', 'jpeg', 'png'];
$bits = explode('.', $target_file['name']);
$file_type = $bits[count($bits) - 1];
if (!in_array($file_type, $allowed_types)) {
$error_msg[$key . '_type'] = $key . ' is a file type that is not allowed.';
} else {
$error_msg[$key . '_type'] = '';
return true;
}

$_SESSION['form_submission_errors'] = $error_msg;
$this->validation_helper->validation_errors;
return false;
}

function _init_picture_settings() {
$picture_settings['max_file_size'] = 5000;
$picture_settings['max_width'] = 9000;
$picture_settings['max_height'] = 9000;
$picture_settings['resized_max_width'] = 450;
$picture_settings['resized_max_height'] = 450;
$picture_settings['destination'] = 'freizas_pics';
$picture_settings['target_column_name'] = 'picture';
$picture_settings['thumbnail_dir'] = 'freizas_pics_thumbnails';
$picture_settings['thumbnail_max_width'] = 120;
$picture_settings['thumbnail_max_height'] = 120;
$picture_settings['upload_to_module'] = true;
return $picture_settings;
}

function _make_sure_got_destination_folders($update_id, $picture_settings) {

$destination = $picture_settings['destination'];

if ($picture_settings['upload_to_module'] == true) {
$target_dir = APPPATH . 'modules/' . segment(1) . '/assets/' . $destination . '/' . $update_id;
} else {
$target_dir = APPPATH . 'public/' . $destination . '/' . $update_id;
}

if (!file_exists($target_dir)) {
//generate the image folder
mkdir($target_dir, 0777, true);
}

//attempt to create thumbnail directory
if (strlen($picture_settings['thumbnail_dir']) > 0) {
$ditch = $destination . '/' . $update_id;
$replace = $picture_settings['thumbnail_dir'] . '/' . $update_id;
$thumbnail_dir = str_replace($ditch, $replace, $target_dir);
if (!file_exists($thumbnail_dir)) {
//generate the image folder
mkdir($thumbnail_dir, 0777, true);
}
}
}
}