QUOTE (uneedawebsite)
I can give you an example that I pulled from my own crontab:
3-58/5 * * * * /usr/bin/php -q -f /home/user/public_html/scripts/run.php
Mark
Syntax that works for me for every 5 minutes is
*/5 * * * * root /path-to-script
Regarding PHP you should be aware of two modes (CLI or command line interface and http/browser mode.
Above example will run the PHP in a shell like environment (CLI) other wise you will need to use lynx -dump URL-to-php or similar means.