This is the recommended way to update feeds. Please use it if you have access to PHP CLI interpreter and can run background processes. You can run single-process update daemon or update_daemon2.php (multi-process, runs several update tasks in parallel) using PHP cli interpreter.
Please do not ever run update daemon or any PHP processes as root. It is recommended, but not required, to run the daemon under your website user id (usually www-data or something like that) to prevent cache file ownership issues.
Run: php ./update.php -daemon (single process) or php ./update_daemon2.php (multi-process)
The script doesn't daemonize (e.g. detach from the terminal). You can force it into background using external utility like start-stop-daemon in Debian. Alternatively, you can run it under screen.