Common DB Framework
Common classes shared between DB Frameworks that want to link between each other.
Getting Started
Common DB is not a database connection itself, instead it serves as a starting point for various DB frameworks. Currently there are two:
- MongoDB Framework
- MySQL Framework
- Coming Soon: Postgres Framework
Default Hierarchy
Any framework will need a Database class that inherits the DB class and handles the connection to the database. Then
there needs to be a default object class that handles specific object related tasks unique to your database type. For
example in MongoDB (a document based database) the default object class is Document all classes using that framework
will inherit from that class. For MySQL the default object class is Row. These classes should also set the $dbClass
static variable to your frameworks class that inherits DB. This allows for dependency injection later on. How the
framework is used from this point is dependant on the framework.
LinkedObject
If setup properly there are helpful classes like LinkedObject which can be used to link a DBObject from one framework/DB to a DBObject from a different framework. Examples can be found in the MongoDB and MySQL frameworks.
Singleton vs Dependency Injection
DB instances can be accessed by using DB::getInstance() which will access a singleton instance of the DB framework.
However Common DB has built in support for Dependency Injection. When in a DBObject class use static::getDBInstance()
to access the DB object being used for that class. This means you can setup a TestDB class that forces a particular output
and then call your default object class setDBInstance() function (i.e. Row::setDBInstance(TestDB::class)) to inject
the dependency. This will setup a singleton, but it will be a new singleton and can be of any class that inherits DB.
