How to update a column after an expiration date in MySQL?

I am working on a laravel 5 app. I have a table with fields like below:

Table Name: applications

• application_status tinyint(1)

• expiration_date datetime (20 days from today)

  1. How can I update the application_status of each row in the table after any expiration_date is passed?
  2. How can I enable that nothing happens when the expiration_date is NULL (The issue is once an application is accepted, the expiration is disabled or set to NULL)

via Chebli Mohamed