Book Image

Persistence in PHP with Doctrine ORM

By : Kevin Dunglas
Book Image

Persistence in PHP with Doctrine ORM

By: Kevin Dunglas

Overview of this book

Doctrine 2 has become the most popular modern persistence system for PHP. It can either be used as a standalone system or can be distributed with Symfony 2, and it also integrates very well with popular frameworks. It allows you to easily retrieve PHP object graphs, provides a powerful object-oriented query language called DQL, a database schema generator tool, and supports database migration. It is efficient, abstracts popular DBMS, and supports PHP 5.3 features. Doctrine is a must-have for modern PHP applications. Persistence in PHP with Doctrine ORM is a practical, hands-on guide that describes the full creation process of a web application powered by Doctrine. Core features of the ORM are explained in depth and illustrated by useful, explicit, and reusable code samples. Persistence in PHP with Doctrine ORM explains everything you need to know to get started with Doctrine in a clear and detailed manner. From installing the ORM through Composer to mastering advanced features such as native queries, this book is a full overview of the power of Doctrine. You will also learn a bunch of mapping annotations, create associations, and generate database schemas from PHP classes. You will also see how to write data fixtures, create custom entity repositories, and issue advanced DQL queries. Finally it will teach you to play with inheritance, write native queries, and use built-in lifecycle events. If you want to use a powerful persistence system for your PHP application, Persistence in PHP with Doctrine ORM is the book you.
Table of Contents (12 chapters)

Implementing inheritance

Like all object-oriented programming languages, PHP is designed on top of the inheritance concept; however, relational databases are not. This is the common problem when mapping classes to tables.

The Doctrine ORM provides the following three ways to achieve inheritance:

  • Mapped Superclasses

  • Single Table Inheritance

  • Class Table Inheritance

To learn about them, we will create three implementations of the same model, that is, for content authors.

Both posts and comments have authors. Authors must have a name and an e-mail address. Posts' authors (and only them) can also have an optional biography.

To represent this, we will create two classes: PostAuthor and CommentAuthor. They both extend an abstract Author class. Each Comment entity is linked to a CommentAuthor class and each Post entity to a PostAuthor class.

Using Mapped Superclasses

Mapped Superclasses are simple PHP classes that share mapped properties used by their descendant entities. Mapped Superclasses are not entities...