setting up a cron job for a PHP script

Hi, I've setup a simple PHP script that runs through a database table and sends an email to a group of members asking them to verify their information. My new ISP allows me to access the cron tab so we can have this script run at set intervals. However I'm a little new to the whole cron tab command line ... is it possible to have a PHP script execute on command from a cron tab? And if so, could someone proide an example of say having the script run on the first of every month? We're using 4.3.0 if that helps. Thanks -Tim