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Best Practices

Here are some best practices you can follow when working with the Doctrine MongoDB ODM.

Don't use public properties on documents

It is very important that you don't map public properties on documents, but only protected or private ones. The reason for this is simple, whenever you access a public property of a proxy object that hasn't been initialized yet the return value will be null. Doctrine cannot hook into this process and magically make the document lazy load.

This can create situations where it is very hard to debug the current failure. We therefore urge you to map only private and protected properties on documents and use getter methods or magic __get() to access them.

Constrain relationships as much as possible

It is important to constrain relationships as much as possible. This means:

  • Impose a traversal direction (avoid bidirectional associations if possible)
  • Eliminate nonessential associations

This has several benefits:

  • Reduced coupling in your domain model
  • Simpler code in your domain model (no need to maintain bidirectionality properly)
  • Less work for Doctrine

Use events judiciously

The event system of Doctrine is great and fast. Even though making heavy use of events, especially lifecycle events, can have a negative impact on the performance of your application. Thus you should use events judiciously.

Use cascades judiciously

Automatic cascades of the persist/remove/merge/etc. operations are very handy but should be used wisely. Do NOT simply add all cascades to all associations. Think about which cascades actually do make sense for you for a particular association, given the scenarios it is most likely used in.

Don't use special characters

Avoid using any non-ASCII characters in class, field, table or column names. Doctrine itself is not unicode-safe in many places and will not be until PHP itself is fully unicode-aware (PHP6).

Initialize collections in the constructor

It is recommended best practice to initialize any business collections in documents in the constructor.


1<?php namespace MyProject\Model; use Doctrine\Common\Collections\ArrayCollection; class User { private $addresses; private $articles; public function __construct() { $this->addresses = new ArrayCollection; $this->articles = new ArrayCollection; } }