Cron Job that runs php script every hour

Hi,

I need help setting up a cron job on a server. The purpose of the cron job is to run a php script every hour. The script deletes the contents of some tables in a mySQL database.

I have tried to use the following (from this tutorial):

curl -s -o /dev/null http://www.domain.com/cleanup.php?clean=log

Even though the script runs nicely if I run it from a browser manually, the cron job doesn't run the script.

I have another cron job that works:

php -f /var/www/domain.com/public_html/shell/indexer.php -- reindexall >/dev/null 2>&1

I don't have access to the cPanel, so I have to tell my web hosting company to set up the job on the server.

Thanks!

Dio