PHP download proxy

<?php
set_time_limit(0);
$url = 'http://mirror.isoc.org.il/pub/fedora/releases/17/Live/x86_64/Fedora-17-x86_64-Live-Desktop.iso';
$file_name = 'Fedora-17-x86_64-Live-Desktop.iso';
header('Content-Type: application/octet-stream');
header("Content-Disposition: attachment; filename=" . $file_name);
ob_end_flush();

// Headers function
// You should able to send from here also the content length header with the data from the headers param but its not working as expected ATM
function handle_headers($ch, $headers) {
    return strlen($headers);
}

// Output function
function output_chunk($ch, $data) {
    echo $data;
    flush();
    return strlen($data);
}


$ch = curl_init($url);
curl_setopt_array($ch, array(
    // CURLOPT_HEADERFUNCTION => 'handle_headers',
    CURLOPT_WRITEFUNCTION => 'output_chunk',
    // CURLOPT_RETURNTRANSFER => true,
    // 1 MB
    CURLOPT_BUFFERSIZE => 500000,
    CURLOPT_HEADER => false
));

curl_exec($ch);