Domain-Driven Design in PHP

Persistence Mechanism Generates Identity

Usually, the simplest way of generating the Identity is to delegate it to the persistence mechanism, because the vast majority of persistence mechanisms support some kind of Identity generation — like MySQL's AUTO_INCREMENT attribute or Postgres and Oracle sequences. This, although simple, has a major drawback: we won't have the Identity of the Entity until we persist it. So to some degree, if we're going with persistence mechanism-generated Identities, we'll couple the Identity operation with the underlying persistence store:

CREATE TABLE `orders` (    `id` int(11) NOT NULL auto_increment,    `amount` decimal (10,5) NOT NULL,    `first_name` varchar(100) NOT NULL,    `last_name` varchar(100) NOT NULL, PRIMARY ...