Checking MySQL database with PHP

[levsha]

Let's say a user submitted some information through a form into a MySQL database.
The data was timestamped.
The user is given a certain number of days to submit an additional chunk of data into the database.
If he doesn't submit it by the required date, an email has to be sent to him with a reminder.
What is the best way to do this?
I'm thinking of automatically running the PHP script once a day.
How do you run scripts automatically on a schedule?
Or is there any better way to do the reminder email?

Thank you!

[ApocDen]

there are many way of doing this. One easy way i can think of is using a cron job

[levsha]

there are many way of doing this. One easy way i can think of is using a cron job

Thank you!
Cron job was the first thing I thought of.