I have previously written a quick post on making files downloadable through PHP scripts. The example in the post reads the file itself into a variable, and as pointed out in the comments, it's not necessarily a very good idea especially if you deal with large files. Recently at work, we needed a reliable way to send files to users' browser, and I decided to take a look at mod_xsendfile, as suggested by Tom Graham.

He starts with some of the benefits of using the xsendfile method over other, more traditional ways. Moving on, he gets to the good stuff - download, installation and a code example of how to use the module (via a X-Sendfile header).

Some days ago I stumbled upon an old entry of Jan in lighty's life, called "X-Sendfile". There he explains how to speed up the delivery of (large) files with lighttpd instead of PHP (YES, lighttpd is very fast - for one customer we created an ImageServer with pure lighty that replaced a 4-server-cluster with Apache and now has 1 server with lighttpd (which is boring around at low load). The box makes 180 Mio. requests per month).

He even gives an example of the functionality, showing how a combination of an entry in the web server's config coupled with a simple PHP script can easily send out a large file to anyone nice and zippy.