rebuildFileCache.php file is a maintenance script to build the file cache for content pages.

$wgUseFileCache must be true for this script to work.

Note that the script will generate the cached files with the same owner as the user running the script. Depending on the file permissions, this may cause permission problems when viewing those pages or when those pages need to be regenerated by normal web browsing. To avoid such problems, it's recommended to run this script as the same user that runs the web server, or fix file owner and permissions once the script finishes.