 <p>If your web server is <a href="http://blog.thinkphp.de/archives/136-Make-the-download-of-large-files-with-PHP-and-lighty-very-easy.html" rel="nofollow noreferrer">lighttpd</a> or <a href="http://www.adaniels.nl/articles/how-i-php-x-sendfile/" rel="nofollow noreferrer">Apache with mod_xsendfile</a>, then you can send the file by specifying a special <code>X-Sendfile</code> header. This allows the web server to make a <code>sendfile</code> call, which can be very, very fast. </p> <p>The reason is <code>sendfile</code> is usually an optimized kernel call which can take bits from the file system and directly put them on a TCP socket. </p>