Using crontab in Linux

 *     *     *     *     *     command to be executed
 -     -     -     -     -
 |     |     |     |     |
 |     |     |     |     +----- day of week (0 - 6) (Sunday=0)
 |     |     |     +------- month (1 - 12)
 |     |     +--------- day of month (1 - 31)
 |     +----------- hour (0 - 23)
 +------------- min (0 - 59)
 

Edit
crontab -e
Example: execute php script every minute
0-59 * * * * php /home/huypv/auto-run.php "param here"

Restart cron daemon
/etc/init.d/crond restart