Q:

Syncing phpMyAdmin databases/tables automatically across two different servers

The Setup:
I am going to set up several websites on different servers. Then, I will create a User Registration System on websites server and export it. Then, I'll upload the same database to all the other websites servers.
So, is there a way to do something where if a person creates an account on one website, it creates an account on all the other websites? Also, the person should be able to login on any of the websites. And everything must be done automatically. I don't want to do stuff manually.

A:

You have these alternatives: 

you use a central authority (user account system). All systems can use that central one to authenticate a users login attempt against or whatever form of authorization is required. That certainly is the preferred approach. 
you replicate (parts of) your database from system to system. That is possible, but less elegant and much more complex. Database replication and the tools required for that are well documented. 
you use some OAuth service, either an existing, known one or you create your own service that is shared between your applications. This is a very powerful and interesting approach. But it only brings advantages if you rely on well known and wide spread services. So for example google or facebook. (Yes, these are those buttons "login with google" you see in many places)

For the central approach from alternative 1 please note that there is no reason why such a system has to be using the same type of database as your applications. In contrary, often other types are much better suited for that purpose. Take a look for example at LDAP servers. 

