File download with curl and php

I have two server1 and server2 servers, server2 only accepts server1 request if it is another ip it returns 404, my site is on server1 and the files for download on server2 , I made the following script to return the server2 :

    ob_start();
    set_time_limit(0);
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
    $r = curl_exec($ch);
    curl_close($ch);
    header('Expires: 0'); // no cache
    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
    header('Last-Modified: ' . gmdate('D, d M Y H:i:s', time()) . ' GMT');
    header('Cache-Control: private', false);
    header('Content-Type: application/force-download');
    header('Content-Disposition: attachment; filename="' . basename($url) . '"');
    header('Content-Transfer-Encoding: binary');
    header('Content-Length: ' . strlen($r)); // provide file size
    header('Connection: close');
    echo $r;

But when the file is too large it displays the following message memory error what would be the solution to this?

Fatal error: Allowed memory size of 268435456 bytes

Do not use PHP to do this, but instead use Apache’s reverse proxy:

Configuration example (part) on server1 :

ProxyPass       /arquivos/  http://server2.example.com/

Or you can work with file types:

<LocationMatch .pdf$>
  ProxyPass http://server2.example.com/
</Locationmatch>

Extra:

If you need IP on the client machine, at server2 , this code will help you:

<?php

echo $_SERVER['REMOTE_ADDR']; // IP do server1

if (array_key_exists('HTTP_X_FORWARDED_FOR', $server)) {
    if (strpos($server['HTTP_X_FORWARDED_FOR'],',') !== false) {
        $server['REMOTE_ADDR'] = current(explode(',', $server['HTTP_X_FORWARDED_FOR']));
    } else {
        $server['REMOTE_ADDR'] = $server['HTTP_X_FORWARDED_FOR'];
    }

    $_SERVER['REMOTE_ADDR'] = $server['REMOTE_ADDR'];
}

echo $_SERVER['REMOTE_ADDR']; // IP do Cliente

What this error means is that you are trying to send bytes of information above the configured limit that is 256 Megabytes .

Try adding this to the top of your code:
ini_set('memory_limit', '-1');

Ref: Memory Limit

If this does not work, you will have to modify your .htaccess file and increase the values for the parameters:
post_max_size = 100M
upload_max_filesize = 100M