Simple PHP daemon which handles database tasks
See example folder. There is an implemantation using Doctrine 2 for persisting and Monolog for logging.
Just run the daemon.php in a own PHP instance.
I suggest using of a tool for daemonizing approaches. Such a tool could be Supervisor. An example config for Supervisor looks like:
[program:daemon]
command=/usr/bin/php /var/www/myproject/daemon/daemon.php
user=www-data
autostart=true
autorestart=true