PHP Doctrine ORM深度指南：从入门到高级
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"Doctrine ORM for PHP" 是一本详细介绍如何在 PHP 中使用 Doctrine ORM 的指南，它提供了一个全面的教程，从入门到高级概念，帮助开发者理解和操作这个强大的数据库抽象层工具。该文档分为多个部分：
1. **简介**：介绍了什么是 Doctrine ORM，它是一个用于 PHP 的对象关系映射 (ORM)，解决传统数据库操作转换为面向对象编程模型的问题。
2. **代码示例**：文档中包含丰富的代码示例，以便读者通过实践学习。
3. **最低要求**：概述了使用 Doctrine ORM 需要的环境和库，包括 PHP 版本、数据库连接要求等。
4. **基本概述**：解释了 ORM 的基本概念，如映射实体（models）、关系管理以及数据持久化。
5. **深入理解 Doctrine**：探讨了关键概念，如连接管理、配置选项、模型定义（列、默认值、数据类型等）和数据库操作（查询、关联关系处理等）。
6. **进一步阅读**：推荐了其他资源供读者进一步探索 Doctrine ORM 的其他特性。
7. **入门指南**：详细步骤指导如何安装、设置环境和运行测试，包括使用 SVN、PEAR 安装器和下载相关包。
8. **连接管理**：讲解了数据库连接的设置、获取和关闭，以及如何与模型关联。
9. **模型定义**：介绍如何根据现有数据库结构生成或手动创建模型，以及定制模型行为。
10. **数据验证和关系**：涉及数据验证规则、不同类型的关联关系（一对一、一对多、多对多等）及其操作。
11. **DQL（Doctrine Query Language）**：展示了如何编写和执行查询语句，包括 SELECT、UPDATE、DELETE 和更复杂的查询构造。
12. **组件概述**：介绍了 Manager、Connection 和其他核心组件的功能和用法。
13. **性能优化和架构**：涵盖了性能提升技巧、技术层面的架构设计以及 Doctrine 的核心组件 DBAL 和 ORM。
14. **异常处理**：讨论了可能遇到的错误和异常类型，以及如何进行适当的处理。
这本书是 PHP 开发者学习和掌握 Doctrine ORM 的宝贵资源，通过一步步的引导，可以有效地提高开发效率和代码质量。
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implementing all the mapping on your own (because at the time of this writing we are not
aware of any powerful ORM tools for PHP that are not based on an ActiveRecord approach).
(1) Note that complexity != size. A domain model can be pretty large without being
complex and vice versa. Obviously, larger domain models have a greater probability of
being complex.
Now you already know a lot about what Doctrine is and what it is not. If you would like to dive
in now and get started right away, jump straight to the next chapter "Getting Started".
Key Concepts
The Doctrine Query Language (DQL) is an object query language. It let's you express queries
for single objects or full object graphs, using the terminology of your domain model: class
names, field names, relations between classes, etc. This is a powerful tool for retrieving or
even manipulating objects without breaking the separation of the domain model (field names,
class names, etc) from the relational model (table names, column names, etc). DQL looks very
much like SQL and this is intended because it makes it relatively easy to grasp for people
knowing SQL. There are, however, a few very important differences you should always keep
in mind:
Take this example DQL query:
FROM User u
LEFT JOIN u.Phonenumbers where u.level > 1
The things to notice about this query:
• We select from classes and not tables. We are selecting from the User class/model.
• We join along associations (u.Phonenumbers)
• We can reference fields (u.level)
• There is no join condition (ON x.y = y.x). The associations between your classes and
how these are expressed in the database are known to Doctrine (You need to make
this mapping known to Doctrine, of course. How to do that is explained later in the
Defining Models (page 51) chapter.).
DQL expresses a query in the terms of your domain model (your classes, the attributes they
have, the relations they have to other classes, etc.).
It's very important that we speak about classes, fields and associations between classes here.
User is not a table / table name . It may be that the name of the database table that the User
class is mapped to is indeed named User but you should nevertheless adhere to this
differentiation of terminology. This may sound nit picky since, due to the ActiveRecord
approach, your relational model is often very similar to your domain model but it's really
important. The column names are rarely the same as the field names and as soon as
inheritance is involved, the relational model starts to diverge from the domain model. You can
have a class User that is in fact mapped to several tables in the database. At this point it
should be clear that talking about "selecting from the User table" is simply wrong then. And
as Doctrine development continues there will be more features available that allow the two
models to diverge even more.
Chapter 1: Introduction 16
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