how to access files which is outside the var folder in linux server in code igniter 3 project

I want to access files which is outside the var folder in linux server and my codeigniter-3 project inside /var/www/html.

and the files inside /data folder.

"/data/admin_assets/upload_files/Photos/nala/start_photo.jpg" that is the path stored in the data base so when i access this url I have get 404- Not found Error

You can use readfile of PHP to read a file and return to browser. An example can be use like this:

<?php

$file = "/data/admin_assets/upload_files/Photos/nala/start_photo.jpg";

if (file_exists($file)) {
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename="'.basename($file).'"');
    header('Expires: 0');
    header('Cache-Control: must-revalidate');
    header('Pragma: public');
    header('Content-Length: ' . filesize($file));
    readfile($file);
    exit;
}
?>

And make sure you set permission so that web server can access that directory: data/admin_assets/upload_files/Photos/nala/