Permission denied Read file on a network drive from php server for which just the user has read access to it

Question

I want to open a file in a network drives with php. The file is not accessible for every one, just for one user. I have the following code:

        $file = "$dir/$fileName";
        $fp = fopen($file, "r");
        if ( !$fp ) {
            throw new Exception('File open failed.');
        }
        $str = stream_get_contents($fp);
        fclose($fp);
        header('Content-type: application/pdf');
        header('Content-Disposition: inline; filename="' . $fileName . '"');
        header('Content-Transfer-Encoding: binary');
        header('Accept-Ranges: bytes');
        exit;

The result: failed to open stream: Permission denied