readmedia.php for Joomla 4 and 5

readmedia.php

<?php
/**
 * @version    1.0.0
 * @package    Readmedia
 * @copyright  Copyright (C) 2018 David Jardin - djumla GmbH
 * @license    GNU GPLv3 <http://www.gnu.org/licenses/gpl.html>
 * @link       http://www.djumla.de
 */

/* Initialize Joomla framework */
define('_JEXEC', 1);

// Load system defines
if (file_exists(dirname(__FILE__) . '/defines.php'))
{
    require_once dirname(__FILE__) . '/defines.php';
}

if (!defined('_JDEFINES'))
{
    define('JPATH_BASE', dirname(__FILE__));
    require_once JPATH_BASE . '/includes/defines.php';
}

require_once JPATH_BASE . '/includes/framework.php';

/* Create the Application */
$container = \Joomla\CMS\Factory::getContainer();

$container->alias('session.web', 'session.web.site')
    ->alias('session', 'session.web.site')
    ->alias('JSession', 'session.web.site')
    ->alias(\Joomla\CMS\Session\Session::class, 'session.web.site')
    ->alias(\Joomla\Session\Session::class, 'session.web.site')
    ->alias(\Joomla\Session\SessionInterface::class, 'session.web.site');

// Instantiate the application.
$app = $container->get(\Joomla\CMS\Application\SiteApplication::class);

// Load the extension Namespaces
\JLoader::register('JNamespacePsr4Map', JPATH_LIBRARIES . '/namespacemap.php');
$extensionPsr4Loader = new \JNamespacePsr4Map();
$extensionPsr4Loader->load();

// Set the application as global app
\Joomla\CMS\Factory::$application = $app;

// Actual permission check starts here

if (!\Joomla\CMS\Factory::getUser()->id)
{
    header("HTTP/1.0 403 access denied");

    echo "Access denied";

    exit();
}

$requestedFile = urldecode(str_replace(\Joomla\CMS\Uri\Uri::root(), "", \Joomla\CMS\Uri\Uri::current()));
$location = dirname(__FILE__) . "/" . $requestedFile;

if (!file_exists($location))
{
    header("HTTP/1.0 404 file not found");

    echo "File not found";

    exit();
}

$size = filesize($location);
$time = date('r', filemtime($location));

$fm = @fopen($location, 'rb');

if (!$fm)
{
    header("HTTP/1.0 505 Internal server error");

    exit();
}

$begin = 0;
$end = $size;

header('HTTP/1.0 200 OK');
header("Content-Type: " . mime_content_type($location));
header('Cache-Control: public, must-revalidate, max-age=0');
header('Pragma: no-cache');
header("Content-Disposition: inline; filename=" . basename($location));
header("Content-Transfer-Encoding: binary\n");
header("Last-Modified: $time");
header('Connection: close');

$cur = $begin;
fseek($fm, $begin, 0);

while (!feof($fm) && $cur < $end && (connection_status() == 0))
{
    print fread($fm, min(1024 * 16, $end - $cur));
    $cur += 1024 * 16;
}

Ist abstrakt schwer zu beantworten, ggf mal den Content-Disposition Header von online zu attachment umstellen.

Bei mir funktioniert es bei Joomla Ver 3.X sowie Joomla 5.x, nachdem ich aber mit verschiedenen Hoster arbeite, hat es anfänglich nicht gefunzt.
Der Grund war, dass es jeweils nginx Server waren, keine Apache, nginx verarbeitet offenbar kein .htaccess und findet deswegen natürlich das Script nicht - also alles paletti, vielleicht sind diese Angaben für einige User interessant
Stefan