from Freshmeat, a good example of integrating PHP with command line
RIBS is an incremental backup system written in PHP which utilizes some common *nix programs (specifically rsync, ssh and cp). Incremental backups mean frequent backups can be done (i.e. hourly) with only around 2x the space of the full backup. Using rsync means that RIBS can act as both a backup script on a local machine, or as a script to backup several network hosts. It is designed to be highly configurable and highly informative to the system administrator. There is a high amount of error checking, and logging/email capabilities.