File is in unknown format when downloading using hidden URL

Question

Every time I use this code and download the file, I get an errors. I assume this is because of the path to the file.

The download.php file is located in /modules/ and is included within index.php on root (inside htdocs/project/) / . The file is located on /modules/download/file.zip

What could be the cause? The URL should be system path? What if I don't want to use system path? Or what is my other issue here?

        $stmt = $this->GetDatabaseConnection()->prepare('SELECT * FROM download_files WHERE id=?');
        $stmt->bind_param('i', $_GET['file']);
        $stmt->execute();
        $stmt->store_result();
        $stmt->bind_result($id, $name, $desc, $filename, $size, $added, $clicks, $uclicks);
        $stmt->fetch();
        if($stmt->num_rows > 0) {
            $fakeFileName= $name . '.zip';
            $realFileName = $filename;
            $file = "download/".$realFileName;
            $fp = fopen($file, 'rb');
            header("Content-Type: application/octet-stream");
            header("Content-Transfer-Encoding: Binary");
            header("Content-Disposition: attachment; filename=$fakeFileName");
            header("Content-Length: " . filesize($file));
            fpassthru($fp);
            exit;
        }
        $stmt->free_result();
        $stmt->close();

Error:

<b>Warning</b>:  fopen(download/6694488-PHPUploadFile.zip): failed to open stream: No such file or directory in <b>C:\xampp\htdocs\project\modules\download.inc.php</b> on line <b>27</b><br />
<br />
<b>Warning</b>:  filesize(): stat failed for download/6694488-PHPUploadFile.zip in <b>C:\xampp\htdocs\project\modules\download.inc.php</b> on line <b>31</b><br />
<br />
<b>Warning</b>:  fpassthru() expects parameter 1 to be resource, boolean given in <b>C:\xampp\htdocs\project\modules\download.inc.php</b> on line <b>32</b><br />

Answer 1

You're using a relative path and fopen() needs an absolute path. Use any of your constants/methods/etc which gives you the absolute path to your project directory to construct the absolute path to your file.
One possibility to do that would be by using the server variables:

$file = $_SERVER['DOCUMENT_ROOT'] . '/modules/download/' . $realFileName;