CakePHP features Controller, Model, and View classes, but it also features some additional classes and objects that make development in MVC a little quicker and more enjoyable. Components, Behaviors, and Helpers are classes that provide extensibility and reusability to quickly add functionality to the base MVC classes in your applications. Right now we’ll stay at a higher level, so look for the details on how to use these tools later on.
Controllers, helpers and models each have a parent class you can use to define application-wide changes. AppController (located at /app/Controller/AppController.php), AppHelper (located at /app/View/Helper/AppHelper.php) and AppModel (located at /app/Model/AppModel.php) are great places to put methods you want to share between all controllers, helpers or models.
Although routes aren’t classes or files, they play a role in requests made to CakePHP. Route definitions tell CakePHP how to map URLs to controller actions. The default behavior assumes that the URL /controller/action/var1/var2 maps to Controller::action($var1, $var2), but you can use routes to customize URLs and how they are interpreted by your application.
Some features in an application merit packaging as a whole. A plugin is a package of models, controllers and views that accomplishes a specific purpose that can span multiple applications. A user management system or a simplified blog might be a good fit for CakePHP plugins.
A Component is a class that aids in controller logic. If you have some logic you want to share between controllers (or applications), a component is usually a good fit. As an example, the core EmailComponent class makes creating and sending emails a snap. Rather than writing a controller method in a single controller that performs this logic, you can package the logic so it can be shared.
Controllers are also fitted with callbacks. These callbacks are available for your use, just in case you need to insert some logic between CakePHP’s core operations. Callbacks available include:
Similarly, Behaviors work as ways to add common functionality between models. For example, if you store user data in a tree structure, you can specify your User model as behaving like a tree, and gain free functionality for removing, adding, and shifting nodes in your underlying tree structure.
Models are also supported by another class called a DataSource. DataSources are an abstraction that enable models to manipulate different types of data consistently. While the main source of data in a CakePHP application is often a database, you might write additional DataSources that allow your models to represent RSS feeds, CSV files, LDAP entries, or iCal events. DataSources allow you to associate records from different sources: rather than being limited to SQL joins, DataSources allow you to tell your LDAP model that it is associated with many iCal events.
Like controllers, models have callbacks:
The names of these methods should be descriptive enough to let you know what they do. You can find the details in the models chapter.
A Helper is a class that aids in view logic. Much like a component used among controllers, helpers allow presentational logic to be accessed and shared between views. One of the core helpers, JsHelper, makes AJAX requests within views much easier and comes with support for jQuery (default), Prototype and Mootools.
Most applications have pieces of view code that are used repeatedly. CakePHP facilitates view code reuse with layouts and elements. By default, every view rendered by a controller is placed inside a layout. Elements are used when small snippets of content need to be reused in multiple views.