How to download file from database folder using php

Question

I want to know how to create a download file from the database/folder. What I want to have is that I have two files butangDonload.php and download.php. When the user clicks the word "download" the pop-up box should appear and save the file. 

The butangDonload.php:

<?php

    $file = "Bang.png"; //Let say If I put the file name Bang.png
    echo "<a href='download.php?nama=".$file."'>donload</a> ";

?>

The download.php:

<?php
    $name= $_GET['nama'];
    download($name);

    function download($name) {
        $file = $nama_fail;

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

Can someone please help me with this?