如何从uploads文件夹下载一个图像,该文件夹放在保存下面程序的地方,php

I have saved an image which is in upload folder, the link is saved in sql table, how should i write a program to download the images from that folder?

for database connection try these codes..

database.php

   <?php
try{
    $db = new PDO('mysql:host=localhost;dbname=database_name', "username" , "password");
    $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

}catch(PDOException $e){
    print "error in connection" . $e->getMessage();
}

now,this php file will access the name of image file stored in database image.php

    <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <?php
    require_once 'database.php';

    $stmt = $db->query("SELECT image_name FROM tablename");
    $row = $stmt->fetchall(PDO::FETCH_ASSOC);
    foreach ($row as $value) {
        $filename = $value['image_name'];



        ?>
        <a href="download.php?id=<?php echo $filename;?>"><?php echo $filename . "<br>";?></a>
        <?php }?>
    </body>
    </html>

download.php

    <?php 

$filename = $_GET["id"];
header('Content-Type: image/jpg');
header('Content-Disposition: attachment; filename="' . basename($filename) . '";');
readfile ($filename);

exit;