In a quick new post to his blog today Slawek looks at a method he's come up with to more efficiently serve up files in a PHP application using the nginx web server.
Sometimes we need to serve files directly from application, especially when file access is restricted by account permissions. Using readfile() to achieve this can successfully kill our web server – even without huge load. To avoid performance problems we can use nginx X-Accel-Redirect feature, and serve files from application through nginx server.
He sets up an example situation - serving up gallery images for a basic site - and shows how to configure the nginx server with the "/gallery" directory and the PHP code you'll need to push the "X-Accel-Redirect" header along with the contents of the image.