class OrderRepository
{
	private $source;

	public function setSource(IOrderSource $source)
	{
		$this->source = $source;
	}

	public function load($orderID)
	{
		return $this->source->load($orderID);
	}
	public function save($order){/*...*/}
	public function update($order){/*...*/}
}

interface IOrderSource
{
	public function load($orderID);
	public function save($order);
	public function update($order);
	public function delete($order);
}

class MySQLOrderSource implements IOrderSource
{
	public function load($orderID);
	public function save($order){/*...*/}
	public function update($order){/*...*/}
	public function delete($order){/*...*/}
}

class ApiOrderSource implements IOrderSource
{
	public function load($orderID);
	public function save($order){/*...*/}
	public function update($order){/*...*/}
	public function delete($order){/*...*/}
}