Enable storage and retrieval (persistence) of counters from a mysql database

[rosenstrauch]

in order to remember changes made to the counter as a developer i want the counters to be persisted to and retrieved from a mysql database.

the app needs to connect to the database and expose routes to allow clients to access counter resources

make sure we are using pdo prepared statements correctly to avoid sql-injection

• http://php.net/manual/en/pdo.prepared-statements.php
• https://phpdelusions.net/pdo#identifiers