Scripts and Web applications using CGI, FastCGI or ISAPI (as well as ASP.NET applications) can accelerate file service by emitting the special CGI header X-Sendfile. Such an acceleration is actually performed by delegating to the low-level parts of the Web server the service of the static file to the client.
For that header to be processed, the script or Web application must be in a script path declared with X-Sendfile Support enabled as outlined in the description of "Script Paths".
Example 6-2. A very simple script taking advanatge of X-Sendfile support (PHP version)
<?php /* Output the special header */ header("X-Sendfile: hello.txt") ?>
The virtual path of the above script should be added to Script Paths. The declared script path should have its X-Sendfile Support enabled and its Files Root Path set to the real directory from which the file hello.txt should be served.