How To Create Plugins

As a working example from the How To Use Plugins section, let’s begin to create a ContactManager plugin. To start out, we’ll set up our plugin’s basic directory structure. It should look like this:

/app
    /Plugin
        /ContactManager
            /Controller
                /Component
            /Model
                /Behavior
            /View
                /Helper
                /Layouts

Note the name of the plugin folder, ‘ContactManager‘. It is important that this folder has the same name as the plugin.

Inside the plugin folder, you’ll notice it looks a lot like a CakePHP application, and that’s basically what it is. You don’t actually have to include any of those folders if you do not use them. Some plugins might only define a Component and a Behavior, and in that case they can completely omit the ‘View’ directory.

A plugin can also have basically any of the other directories that your application can, such as Config, Console, Lib, webroot, etc.

Note

If you want to be able to access your plugin with a URL, defining an AppController and AppModel for the plugin is required. These two special classes are named after the plugin, and extend the parent application’s AppController and AppModel. Here’s what they should look like for our ContactManager example:

// In /app/Plugin/ContactManager/Controller/ContactManagerAppController.php

class ContactManagerAppController extends AppController {
}
// In /app/Plugin/ContactManager/Model/ContactManagerAppModel.php

class ContactManagerAppModel extends AppModel {
}

If you forgot to define these special classes, CakePHP will hand you “Missing Controller” errors until you’ve done so.

Please note that the process of creating plugins can be greatly simplified by using the Cake shell.

In order to bake a plugin please use the following command:

user@host$ cake bake plugin ContactManager

Now you can bake using the same conventions which apply to the rest of your app. For example - baking controllers:

user@host$ cake bake controller Contacts --plugin ContactManager

Please refer to the chapter Code Generation with Bake if you have any problems with using the command line.

Warning

Plugins do not work as namespacing to separate code. Due to PHP lacking namespaces in older versions you cannot have the same class, or same filename, in your plugins. Even if it is two different plugins. So use unique classes and filenames, possible prefixing the class and filename with the plugin name.

Plugin Controllers

Controllers for our ContactManager plugin will be stored in /app/Plugin/ContactManager/Controller/. Since the main thing we’ll be doing is managing contacts, we’ll need a ContactsController for this plugin.

So, we place our new ContactsController in /app/Plugin/ContactManager/Controller and it looks like so:

// In app/Plugin/ContactManager/Controller/ContactsController.php

class ContactsController extends ContactManagerAppController {
    public $uses = array('ContactManager.Contact');

    public function index() {
        // ...
    }
}

Note

This controller extends the plugin’s AppController (called ContactManagerAppController) rather than the parent application’s AppController.

Also note how the name of the model is prefixed with the name of the plugin. This is required to differentiate between models in the plugin and models in the main application.

In this case, the $uses array would not be required as ContactManager.Contact would be the default model for this controller, however it is included to demonstrate how to properly prepend the plugin name.

If you want to access what we’ve got going thus far, visit /contact_manager/contacts. You should get a “Missing Model” error because we don’t have a Contact model defined yet.

Plugin Models

Models for the plugin are stored in /app/Plugin/ContactManager/Model. We’ve already defined a ContactsController for this plugin, so let’s create the model for that controller, called Contact:

// In /app/Plugin/ContactManager/Model/Contact.php

class Contact extends ContactManagerAppModel {
}

Visiting /contact_manager/contacts now (given you’ve got a table in your database called ‘contacts’) should give us a “Missing View” error. Let’s create that next.

Note

If you need to reference a model within your plugin, you need to include the plugin name with the model name, separated with a dot.

For example:

// In /app/Plugin/ContactManager/Model/Contact.php

class Contact extends ContactManagerAppModel {
    public $hasMany = array('ContactManager.AltName');
}

If you would prefer that the array keys for the association not have the plugin prefix on them, use the alternative syntax:

// In /app/Plugin/ContactManager/Model/Contact.php

class Contact extends ContactManagerAppModel {
    public $hasMany = array(
        'AltName' => array(
            'className' => 'ContactManager.AltName'
        )
    );
}

Plugin Views

Views behave exactly as they do in normal applications. Just place them in the right folder inside of the /app/Plugin/[PluginName]/View/ folder. For our ContactManager plugin, we’ll need a view for our ContactsController::index() action, so let’s include that as well:

<!-- /app/Plugin/ContactManager/View/Contacts/index.ctp: -->
<h1>Contacts</h1>
<p>Following is a sortable list of your contacts</p>
<!-- A sortable list of contacts would go here....-->

Note

For information on how to use elements from a plugin, look up Elements

Overriding Plugin Views From Inside Your Application

You can override any plugin views from inside your app using special paths. If you have a plugin called ‘ContactManager’ you can override the view files of the plugin with more application specific view logic by creating files using the following template “app/View/Plugin/[Plugin]/[Controller]/[view].ctp”. For the Contacts controller you could make the following file:

/app/View/Plugin/ContactManager/Contacts/index.ctp

Creating this file, would allow you to override “/app/Plugin/ContactManager/View/Contacts/index.ctp”.

Plugin Assets

A plugin’s web assets (but not PHP files) can be served through the plugin’s ‘webroot’ directory, just like the main application’s assets:

app/Plugin/ContactManager/webroot/
                                    css/
                                    js/
                                    img/
                                    flash/
                                    pdf/

You may put any type of file in any directory, just like a regular webroot.

But keep in mind that handling static assets, such as images, Javascript and CSS files of plugins, through the Dispatcher is incredibly inefficient. It is strongly recommended to symlink them for production. For example like this:

ln -s app/Plugin/YourPlugin/webroot/css/yourplugin.css app/webroot/css/yourplugin.css

Linking to Assets in Plugins

Simply prepend /plugin_name/ to the beginning of a request for an asset within that plugin, and it will work as if the asset were in your application’s webroot.

For example, linking to ‘/contact_manager/js/some_file.js’ would serve the asset ‘app/Plugin/ContactManager/webroot/js/some_file.js’.

Note

It is important to note the /your_plugin/ prefix before the asset path. That makes the magic happen!

Changed in version 2.1: Use plugin syntax to request assets. For example in your View:

<?php echo $this->Html->css("ContactManager.style"); ?>

Components, Helpers and Behaviors

A plugin can have Components, Helpers and Behaviors just like a regular CakePHP application. You can even create plugins that consist only of Components, Helpers or Behaviors which can be a great way to build reusable components that can easily be dropped into any project.

Building these components is exactly the same as building it within a regular application, with no special naming convention.

Referring to your component from inside or outside of your plugin requires only that you prefix the plugin name before the name of the component. For example:

// Component defined in 'ContactManager' plugin

class ExampleComponent extends Component {
}

// Within your controllers:

public $components = array('ContactManager.Example');

The same technique applies to Helpers and Behaviors.

Note

When creating Helpers you may find AppHelper is not automatically available. You should declare the resources you need with Uses:

// Declare use of AppHelper for your Plugin's Helper

App::uses('AppHelper', 'View/Helper');

Expand Your Plugin

This example created a good start for a plugin, but there is a lot more that you can do. As a general rule, anything you can do with your application, you can do inside of a plugin instead.

Go ahead, include some third-party libraries in ‘Vendor’, add some new shells to the cake console, and don’t forget to create test cases so your plugin users can automatically test your plugin’s functionality!

In our ContactManager example, we might create add/remove/edit/delete actions in the ContactsController, implement validation in the Contact model, and implement the functionality one might expect when managing their contacts. It’s up to you to decide what to implement in your plugins. Just don’t forget to share your code with the community so that everyone can benefit from your awesome, reusable components!

Plugin Tips

Once a plugin has been installed in /app/Plugin/, you can access it at the URL /plugin_name/controller_name/action. In our ContactManager plugin example, we’d access our ContactsController at /contact_manager/contacts.

Some final tips on working with plugins in your CakePHP applications:

  • When you don’t have a [Plugin]AppController and [Plugin]AppModel, you’ll get missing Controller errors when trying to access a plugin controller.
  • You can define your own layouts for plugins, inside app/Plugin/[Plugin]/View/Layouts. Otherwise, plugins will use the layouts from the /app/View/Layouts folder by default.
  • You can do inter-plugin communication by using $this->requestAction('/plugin_name/controller_name/action'); in your controllers.
  • If you use requestAction, make sure controller and model names are as unique as possible. Otherwise you might get PHP “redefined class ...” errors.
  • When adding routes with extensions to your plugin, ensure you use Router::setExtensions() so you do not override application routing.

Publish Your Plugin

You can add your plugin to plugins.cakephp.org or propose it to the awesome-cakephp list.

Also, you might want to create a composer.json file and publish your plugin at packagist.org. This way it can easily be used through Composer.

Choose a semantically meaningful name for the package name. This should ideally be prefixed with the dependency, in this case “cakephp” as the framework. The vendor name will usually be your GitHub username. Do not use the CakePHP namespace (cakephp) as this is reserved to CakePHP owned plugins. The convention is to use lowercase letters and dashes as separator.

So if you created a plugin “Logging” with your GitHub account “FooBar”, a good name would be foo-bar/cakephp-logging. And the CakePHP owned “Localized” plugin can be found under cakephp/localized respectively.