Manual

Connection types

One to one

One to one connection is the simplest one. Basically it describes a cohesion where One object contains one single instance of another object. Like for example a car has one owner. The simplest way to implement this in the database would be to have a table for the Owner which would have one column that references to the car-table's id-column. We make the reference unique to have each car have only one owner.

class OwnerPersistence extends PersistenceObject {
	
	public function OwnerPersistence() {
		
		$this->tableName = "owner";
		$this->className = "Owner";
		
		$this->addOneToOnePropertyDescription("car", "id", "owner", "car_id", "Car");
		
		parent::PersistenceObject(func_get_args());

	}
}

class CarPersistence extends PersistenceObject {
	
	public function CarPersistence() {
		
		$this->tableName = "car";
		$this->className = "Car";
		
		$this->addOneToOnePropertyDescription("owner", "car_id", "owner", "id", "Owner");
		
		parent::PersistenceObject(func_get_args());

	}
}

Another way to implement this is to create a connection table for the property and set the owner id as unique and car id as unique.

And in code:

class OwnerPersistence extends PersistenceObject {
	
	public function OwnerPersistence() {
		
		$this->tableName = "owner";
		$this->className = "Owner";
		
		$this->addOneToOnePropertyDescription("car", "owner_id", "owner_car", "car_id", "Car");
		
		parent::PersistenceObject(func_get_args());

	}
}

class CarPersistence extends PersistenceObject {
	
	public function CarPersistence() {
		
		$this->tableName = "car";
		$this->className = "Car";
		
		$this->addOneToOnePropertyDescription("owner", "car_id", "owner_car", "owner_id", "Owner");
		
		parent::PersistenceObject(func_get_args());

	}
}

Codewise the difference between the two methods is not much. But in databaselevel while the first method is easier, the latter is more versatile when there is need to make changes.