Models play a key role in nearly every web application. Their main purpose is to abstract business logic and database operations from higher levels (controllers and views). They also act as a gatekeeper and—if properly implemented—make sure that only valid and allowed data gets passed through them. Models in li3 have three main purposes:

  1. Provide an abstraction layer to the underlying data source(s)
  2. Perform common data operations (like fetching and storing data)
  3. Help with validating data.

Also, li3 makes it easy to extend models so that they fit your application's needs. Thanks to the nifty autoloading mechanism, models are lazy-loaded and are only initialized when you need them. In the next sections you will learn how to use models and perform common operations on them. Later sections will provide you with a more detailed look on models like relationships between them and how to extend models to fit your application's needs.

The Model class is the starting point for the domain logic of your application. Models are tasked with providing meaning to otherwise raw and unprocessed data (e.g. user profile). Models expose a consistent and unified API to interact with an underlying datasource (e.g. MongoDB, CouchDB, MySQL) for operations such as querying, saving, updating and deleting data from the persistent storage.

As the framework is capable of working with document oriented data sources as it is with relational databases, we use the term entity to refer to what might be considered a document in one data source type or a record/row in another type.

Models allow you to interact with your data in two fundamentally different ways: querying and data mutation (saving/updating/deleting). All query-related operations may be done through the static find() method, along with some additional utility methods provided for convenience. Classes extending the Model class should, conventionally, be named as plural, CamelCase and be placed in the models directory. i.e. a posts model would be model/Posts.php.

Where To Go Next

Read the section below on how to create a model first, then continue with a quick look into the basics of creating connections, creating/updating/deleting entites in data mutation, persisting entities by saving them to the datastore. Finally querying shows how to get all the precious data back.

Creating a Model

li3 provides you with a general-purpose class that all your models should extend. You can find the Model class in the lithium\data namespace. If you do nothing more than extend it, you instantly get a bunch of functionality that covers basic CRUD as well as more complex tasks.

Let's say you want to store and manage blog posts in your database. According to our conventions, you create a new file called Posts.php in app/models. The basic structure looks like this:

namespace app\models;

class Posts extends \lithium\data\Model {}
li3 also allows model creation via the console: You can enter li3 create model Posts into the command line (assuming you have configured the command line for use) and the code above will automatically be created in a file called \app\models\Posts.php.