currently I am developing an app for my final class in college. The concept of the app is a Contact keeping app, essentially a user will be greeted by a login screen where they can either login if they already have an account or register if they don't. When you register the user will be prompt to enter their name, username, password and email. They then submit it and they will again be greeted by the login screen where they can now login in with their recently created credentials. Once they login successfully they be be show an Activity that welcomes them with their name that is retrieved from the table in the database by matching the username and password on the login, it retrieves all the information in that row. I pretty much have that down but what I am having trouble with is where am I going to hold the contacts that the users wants to save, I know that is has to be in another table but how am I going to set it up so I can match the a certain user to all of their contacts in the other table.

Once I get that information I need to put it on a ListView so the user can see their contacts and scroll through them, they can then add, delete or edit them. 

As of right now I am able to register, login and display the welcome screen with no problem now I just need to be able to add, delete and edit contacts.

Java is used for the Android Studio part and PHP is used for the file that make the connection in the host online. 

I am using Volley and JSON request.

The database and PHP files that make the request to the database are hosted in 000webhost.