Check for remote file and force the user to download if it exists.

force-download-remote-file.php

$file = 'http://www.example.com/path/to/file.ext';

$headers = array_change_key_case(get_headers($file, TRUE));

$filesize = $headers['content-length'][1];

if ( $headers[0] != 'HTTP/1.1 404 Not Found' ) {
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename='.basename($file));
    header('Content-Transfer-Encoding: binary');
    header('Expires: 0');
    header('Cache-Control: must-revalidate');
    header('Pragma: public');
    header('Content-Length: ' . $filesize);
    echo "downloading";
    ob_clean();
    flush();
    readfile($file);
    exit;
}

while(1) {
    Echo "\n";
    if ( connection_status() != 0 ) {
        die;
    }
}

is there a way it download file in chunk and deliver in chunk? so no memory overflow?

This works but I had to replace $filesize = $headers['content-length'][1]; with $filesize = $headers['content-length'];