If its running on linux, the php interpreter can be called as the cli version just the same.
an sample crontab for running a script nightly would be
0 0 * php -f /path/to/script.php
The crontab format is
minute hour day of month month day of week 'command'
0-59 0-24 1-31 1-12 0-6
So you can have something like
0 17 5 php -f /script.php # run at 5PM every Friday
/5 1-5 php -f /script2.php # run every 5 minutes monday - friday