As it is your website, According your requirement you shall use cron job from your cpanel.
It will put the direct entries in the table that you wanted to save.
You should save the text that is to be stored in the table (i.e., content to be saved) inside the cron.php (or any name that you prefer)
and then form your cpanel you should set the time when the file should be executed
/home/username/public_html/cron/cron.php
Here is the rough syntax :
minute hour day month day-of-week command-line-to-execute
You can choose the time your file should be executed from cpanel itself.
Here is the link to learn more about cron job