The format is something like this. Eactly the same as if you were trying to run the command from the terminal.
php_location full_script_location output_location
So for example on my server I would use something like this:
/usr/bin/php /home/yacoby/status/check.php
You need to make sure your email address is set correctly.
If you don't want it to email you the output from the script (i.e. you want to log it, or do the emailing from within the script), put > /dev/null at the end of the command. eg.
/usr/bin/php /home/yacoby/status/check.php > /dev/null