Modeling Data with PHPCR-ODM

The Doctrine PHPCR-ODM is a doctrine object-mapper on top of the PHP Content Repository (PHPCR), which is a PHP adaption of the JSR-283 specification. The most important feature of PHPCR is the tree structure to store the data. All data is stored in items of a tree, called nodes. You can think of this like a file system, that makes it perfect to use in a CMS.

On top of the tree structure, PHPCR also adds features like searching, versioning and access control.

Doctrine PHPCR-ODM has the same API as the other Doctrine libraries, like the Doctrine ORM. The Doctrine PHPCR-ODM adds another great feature to PHPCR: multi-language support.

A Simple Example: A Task

The easiest way to get started with the PHPCR-ODM is to see it in action. In this section, you are going to create a Task object and learn how to persist it.

Creating a Document Class

Without thinking about Doctrine or PHPCR-ODM, you can create a Task object in PHP:

// src/App/Document/Task.php
namespace use App\Document;

class Task
{
    protected $description;

    protected $done = false;
}

This class - often called a "document" in PHPCR-ODM, meaning a basic class that holds data - is simple and helps fulfill the business requirement of needing tasks in your application. This class can't be persisted to Doctrine PHPCR-ODM yet - it's just a simple PHP class.

A Document is analogous to the term Entity employed by the Doctrine ORM. To have the mapping happen automatically, place your documents in the Document namespace within your application.

Add Mapping Information

Doctrine allows you to work with PHPCR in a much more interesting way than just fetching data back and forth as an array. Instead, Doctrine allows you to persist entire objects to PHPCR and fetch entire objects out of PHPCR. This works by mapping a PHP class and its properties to the PHPCR tree.

For Doctrine to be able to do this, you just have to create "metadata", or configuration that tells Doctrine exactly how the Task document and its properties should be mapped to PHPCR. This metadata can be specified in a number of different formats including YAML, XML or directly inside the Task class via attributes:

1// src/App/Document/Task.php namespace App\Document; use Doctrine\ODM\PHPCR\Mapping\Attributes as PHPCR; #[PHPCR\Document] class Task { #[PHPCR\Id] private $id; #[PHPCR\Field(type: 'string')] private $description; #[PHPCR\Field(type: 'boolean')] private $done = false; #[PHPCR\ParentDocument] private $parentDocument; }
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After this, you have to create getters and setters for the properties.

This Document uses the parent document and a node name to determine its position in the tree. Because there isn't any name set, it is generated automatically. If you want to use a specific node name, such as a slugified version of the title, you need to add a property mapped as Nodename.

A Document must have an id property. This represents the full path (parent path + name) of the Document. This will be set by Doctrine by default and it is not recommend to use the id to determine the location of a Document.

For more information about identifier generation strategies, refer to the doctrine documentation

You may want to implement Doctrine\ODM\PHPCR\HierarchyInterface to expose the hierarchy in a standardized way.

You can also check out Doctrine's Basic Mapping Documentation for all details about mapping information. If you use attributes, you'll need to prepend all attributes with PHPCR\, which is the name of the imported namespace (e.g. #[PHPCR\Document(..)]), this is not shown in Doctrine's documentation. You'll also need to include the use Doctrine\ODM\PHPCR\Mapping\Attributes as PHPCR; statement to import the PHPCR attributes prefix.

Persisting Documents to PHPCR

Now that you have a mapped Task document, complete with getter and setter methods, you are ready to persist data to PHPCR. For a simple example, lets do this from inside a controller:

// src/App/Controller/DefaultController.php

// ...
use App\Document\Task;
use Doctrine\ODM\PHPCR\DocumentManagerInterface;
use Symfony\Component\HttpFoundation\Response;

// ...
public function createAction(DocumentManagerInterface $documentManager)
{
    $rootTask = $documentManager->find(null, '/tasks');

    $task = new Task();
    $task->setDescription('Finish CMF project');
    $task->setParentDocument($rootTask);

    $documentManager->persist($task);

    $documentManager->flush();

    return new Response('Created task "'.$task->getDescription().'"');
}

Take a look at the previous example in more detail:

  • line 8 We use symfony controller injection with autowiring to get the document manager. This service is responsible for storing and fetching objects to and from PHPCR.
  • line 10 This line loads the root document for the tasks, as each PHPCR document needs to have a parent. To create this root document, you can configure a Repository Initializer, which will be executed when running doctrine:phpcr:repository:init.
  • lines 12-14 In this section, you instantiate and work with the $task object like any other, normal PHP object.
  • line 16 The persist() method tells Doctrine to "manage" the $task object. This does not actually cause a query to be made to PHPCR (yet).
  • line 20 When the flush() method is called, Doctrine looks through all of the objects that it is managing to see if they need to be stored to PHPCR. In this example, the $task object has not been saved yet, so the document manager makes a query to PHPCR to add it.

When creating or updating objects, the workflow is always the same. In the next section, you'll see how Doctrine is smart enough to update documents if they already exist in PHPCR.

Fetching Objects from PHPCR

Fetching an object back out of PHPCR is even easier. For example, suppose you've configured a route to display a specific task by name:

use App\Document\Task;
use Doctrine\ODM\PHPCR\DocumentManagerInterface;

public function showAction(DocumentManagerInterface $documentManager, $name)
{
    $repository = $documentManager->getRepository(Task::class);
    $task = $repository->find('/tasks/'.$name);

    if (!$task) {
        throw $this->createNotFoundException('No task found with name '.$name);
    }

    return new Response('['.($task->isDone() ? 'x' : ' ').'] '.$task->getDescription());
}

To retrieve objects from the document repository using both the find and findMany methods and all helper methods of a class-specific repository. In PHPCR, it's often unknown for developers which node has the data for a specific document, in that case you should use the document manager to find the nodes (for instance, when you want to get the root document). In example above, we know they are Task documents and so we can use the repository.

The repository contains all sorts of helpful methods:

// query by the id (full path)
$ task = $repository->find($id);

// query for one task matching be name and done
$ task = $repository->findOneBy(['name' => 'foo', 'done' => false]);

// query for all tasks matching the name, ordered by done
$ tasks = $repository->findBy(
    ['name' => 'foo'],
    ['done' => 'ASC']
);

If you use the repository class, you can also create a custom repository for a specific document. This helps with "Separation of Concern" when using more complex queries. This is similar to how it's done in Doctrine ORM, for more information read "Custom Repository Classes" in the core documentation.

You can also query objects by using the Query Builder provided by Doctrine PHPCR-ODM. For more information, read the QueryBuilder documentation.

Updating an Object

Once you've fetched an object from Doctrine, updating it is easy. Suppose you have a route that maps a task ID to an update action in a controller:

use App\Document\Task;
use Doctrine\ODM\PHPCR\DocumentManagerInterface;

public function updateAction(DocumentManagerInterface $documentManager, $name)
{
    $repository = $documentManager->getRepository(Task::class);
    $task = $repository->find('/tasks/'.$name);

    if (!$task) {
        throw $this->createNotFoundException('No task found for name '.$name);
    }

    if (!$task->isDone()) {
        $task->setDone(true);
    }

    $documentManager->flush();

    return new Response('[x] '.$task->getDescription());
}

Updating an object involves just three steps:

  1. fetching the object from Doctrine;
  2. modifying the object;
  3. calling flush() on the document manager

Notice that calling $documentManger->persist($task) isn't necessary. Recall that this method simply tells Doctrine to manage or "watch" the $task object. In this case, since you fetched the $task object from Doctrine, it's already managed.

Deleting an Object

Deleting an object is very similar, but requires a call to the remove() method of the document manager after you fetched the document from PHPCR:

$ documentManager->remove($task);
$ documentManager->flush();

As you might expect, the remove() method notifies Doctrine that you'd like to remove the given document from PHPCR. The actual delete operation however, is not actually executed until the flush() method is called.

Summary

With Doctrine, you can focus on your objects and how they're useful in your application and worry about database persistence second. This is because Doctrine allows you to use any PHP object to hold your data and relies on mapping metadata information to map an object's data to a particular database table.

And even though Doctrine revolves around a simple concept, it's incredibly powerful, allowing you to create complex queries and subscribe to events that allow you to take different actions as objects go through their persistence lifecycle.