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Persistence in PHP with Doctrine ORM

Chapter 2. Entities and Mapping Information

In the previous chapter, we discovered the concepts behind Doctrine, we learned how to use Composer to install it, we set up the Doctrine Command Line Tools and we dived into the Entity Manager.

In this chapter, we will cover the following topics:

Creating our first entity class
Mapping it to its related database table and columns with annotations
Using a command helper provided by Doctrine to automatically generate the database schema
Creating some fixtures data and dealing with the Entity Manager to display our data in a web user interface

Because we are building a blog, our main entity class will be called Post, as shown in the following figure:

Our Post entity class has the following four properties:

id: The unique identifier of the post across the database table (and the blog)
title: The post's title
body: The post's body
publicationDate: The date of publication of the post

Understanding Doctrine Mapping Types

Doctrine Mapping Types used in the @Column annotation are neither SQL types nor PHP types but they are mapped to both. For instance, the Doctrine text type will be casted to the string PHP type in the entity and stored in a database column with the CLOB type.

The following is a correspondence table for Doctrine Mapping Type of PHP type and SQL type:

Doctrine Mapping Type	PHP Type	SQL Type
`string`	`string`	`VARCHAR`
`integer`	`integer`	`INT`
`smallint`	`integer`	`SMALLINT`
`bigint`	`string`	`BIGINT`
`boolean`	`boolean`	`BOOLEAN`
`decimal`	`double`	`DECIMAL`
`date`	`\DateTime`	`DATETIME`
`time`	`\DateTime`	`TIME`
`datetime`	`\DateTime`	`DATETIME` or `TIMESTAMP`
`text`	`string`	`CLOB`
`object`	object using the `serialize()` and `unserialize()` methods	`CLOB`
`array`	`array` using `serialize()` and `unserialize()` methods	`CLOB`
`float`	`double`	`FLOAT` (double precision)
`simple_array`	`array` using `implode()` and `explode()` ...

Key benefits

Develop a fully functional Doctrine-backed web application

Demonstrate aspects of Doctrine using code samples

Generate a database schema from your PHP classes

Description

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.

Who is this book for?

This book is primarily intended for PHP developers and architects who want to increase their skills in the field of Persistence and ORM to map the data they are working on to objects they are using in programming. Basic knowledge of databases and PDO and working knowledge of PHP namespaces is a prerequisite.

What you will learn

Install Doctrine through the Composer dependency manager

Configure Doctrine Command Line Tools

Learn to manage relations between entities with different association types

Create data fixtures, a custom entity repository, and native SQL queries

Master the query builder to generate DQL queries

Get started with inheritance and lifecycle events

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M. Finnerty Jr. Nov 22, 2015

Great book. Well written. I would recommend this book to anyone staring with ORM's

Amazon Verified review

Derek J. Lambert Mar 13, 2014

If you're looking for a definitive, all-encompassing API reference for the Doctrine libraries this book most likely won't meet your needs. For those discovering the power and freedom provided by the Doctrine ORM library for the first time or struggling to put all the pieces together using project documentation, Stack Overflow, and the other usual suspects - this book is for you! Throw in a little object-orientated PHP and you're well on your way to building a functional, usable, and extendable application.Dunglas begins with a brief but sufficient stop explaining the prerequisites for a modern PHP 5.4+ project, utilizing Composer to provide the Doctrine 2.4 and related dependencies. As he builds a mock application the code samples are provided in the context of a plausible real-world use scenario, and built upon while progressing through the entire object graph. This perspective provides a clear understanding of object associations and collections.Dunglas goes on to describe using entity repositories and Query Builder to access and manipulate stored entities, continuing into the Doctrine Query Language (DQL) for custom queries. He finishes off exploring some of the advanced functionality provided including object inheritance, events, and native queries.While the subject of unit tests are never touched, functional testing is covered within the scope of the ever useful data fixture. A plethora of additional advanced and tangential subjects, while beyond the extent of the text, are brought up in context with a brief summary and URL for authoritative documentation allowing further exploration into unlimited possibilities.Persistence in PHP with Doctrine ORM fills a long lacking void and provides a coherent and fluent tutorial on the current Doctrine 2 codebase. I can’t imagine where I’d be on my current projects had I started with an up to date reference a couple years ago!

J Aug 03, 2015

This was one of the best technical books I've read. The author did a remarkable job at keeping the depth at the just the right level where you gain understanding, but not get bored of needless details.

proappstore Jan 20, 2020

Straight forward. Excellent!

A. Zubarev Feb 16, 2014

In short, Persistence in PHP with Doctrine ORM is a book about harnessing the power of Doctrine ORM, but also:Will let you build a working project using Doctrine involving advanced techniques;Will guard you from doing mistakes early in your getting known Doctrine, andWill advocate on appropriate technologies to use in addition in case your next creation is going to see the world.I would recommend this book to a developer who worked with PHP already, but getting ready to embark onto a more intensive data processing endeavor.The book is not terribly long, yet comprehensive enough to allow a person to become proficient in Doctrine say overnight (yes, my Kindle app estimated my reading speed at ~ 2.5 Hrs, that is without me experimenting with code). Personally, I value concise books because they give me a push and allow a relatively comfortable solo sailing with an occasional exploration of a topic I did not encounter learning but stumbled upon doing real-life work.As an aside, use of an ORM (not just Doctrine specifically) is typically being perceived as a negative phenomenon by the data people (disclaimer: I am the data person), unsurprisingly Kevin mentions performance implications under the so called Big Data scenario. This has it’s grounds, I agree, as for example tuning DML or data retrieval, so let’s not argue here, but at least one aspect on an ORM not possible to beat – is its ability to allow seamless transition from one database platform to another, relatively uncommon in the past, seems to being picking up nowadays. But do not be overly optimistic, no migration is ever smooth, it just alleviates some of the pains and minimizes the costs of engineering and maintaining your software.On the not so bright side the author does not cover executing stored procedures/packages, and apparently Doctrine (as most OSS projects) has a long list of defects, yeah, I can hear you, this is a book review, nothing else, ditto.So one last interesting discovery, the Doctrine community focuses more and more on a NoSQL, Mongo in particular, which is thrilling.You will find information in the book on how to build your own SQL, implement association, inheritance and even a not so often used many-to-many relationships.On the odd note, I saw a circular reference created in one of the book examples, while possible it is very dangerous! Also the book covers only one approach: building your app code-first: meaning the database schema is created after a class, which I (you know who am I Smile) don’t endorse, alas I am / was new to Doctrine.I suggest Kevin adds to ver. 2.0 of this book the following:Building an application the schema-up way, too, andProvide an example where Doctrine is using a Mongo database.I give this book a 5 out of 5 rating because it has achieve its objectives, however it seems that Packt could give it the “Instant” moniker due to its material coverage.

Persistence in PHP with Doctrine ORM: This book is designed for PHP developers and architects who want to modernize their skills through better understanding of Persistence and ORM. You'll learn through explanations and code samples, all tied to the full development of a web application.

What do you get with Print?

Persistence in PHP with Doctrine ORM

Chapter 2. Entities and Mapping Information

Creating the Entity class

Note

Generating getters and setters

Note

Mapping with Doctrine annotations

Knowing about the @Entity annotation

Understanding the @Table, @Index, and @UniqueConstraint annotations

Understanding Doctrine Mapping Types

Creating the database schema

Note

Installing Data fixtures

Note

Creating a simple UI

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Persistence in PHP with Doctrine ORM: This book is designed for PHP developers and architects who want to modernize their skills through better understanding of Persistence and ORM. You'll learn through explanations and code samples, all tied to the full development of a web application.

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