'Follow' or 'Subscribe' method

I want to know how Follow system in Twitter or Subscribe in Youtube method in PHP and MySQL. How it is work in the database?

Do I have to create "subscribes" table which contain information for a user that following a content/other user's publication.

E.g If someone follow/sub someone, my app create a new row in the table e开发者_如何学Pythonxample user:userA action:follow who:userB

So if userA open userB's content, I have to search this table if userA already follow userB or not? Or there are easier method?

Thanks.

For an easy subscription System:

table_user

• id
• name

table_subscriber

• id_user_subscriber -> points to table_user -> id
• id_user_provider -> points to table_user -> id

if you want to keep track if the subscriber has seen the new post alredy, you have to create another table:

table_post

• id
• name

table_subscriber_post

• id_user_subscriber -> points to table_user -> id
• id_post -> points to table_post -> id

If the user has seen the post, create an entry in the table above