Developing our first plugin

4th March, 2019 in #Plugins

This article is part of the Our first plugin series

In this article, we’ll create a simple plugin that displays some text in a template. We can then build on these basic concepts to make a more complex plugin in part 2.

Giving the plugin a name

The first decision when creating a plugin is to give it a name. We’ll call our’s “Hello World”. From this we can generate a short name - this must be lowercase alphanumeric text with underscores replacing spaces (often called Snake case). So “Hello World” becomes “hello_world”.

This will define:

• the template tag (eg, {exp:hello_world})
• the plugin’s folder name (eg, hello_world)
• the name of the plugin file (eg, pi.hello_world.php)

Creating the plugin’s file structure

From EE 3 onwards, all plugins also need to be in their own folder containing an addon.setup.php file and the plugin file itself and must be installed from the Add-ons section.

First let’s create a folder for the plugin: hello_world. In that folder we create the addon.setup.php file:

<?php

return array(
    'name'        => 'Hello World',
    'description' => 'My first plugin',
    'author'      => 'EE Recipes',
    'author_url'  => 'https://ee-recipes.com/',
    'version'     => '1.0.0',
    'namespace'   => 'EeRecipes\HelloWorld',
);

Most of these settings are obvious, except perhaps the namespace. This is a unique value (to your add-on) that EE uses to prevent any of your code from getting confused with other add-ons. Typically, this will be a combination of your name or company and the add-on name. There should be no spaces and words are capitalised. (More on namespaces.)

We can then create an empty, main plugin file, pi.hello_world.php:

<?php

class Hello_World {

    public function __construct()
    {

    }

}

// End of file pi.hello_world.php

Displaying some text

The plugin outputs the template text by returning the value from the class. To return a value from the constructor method, we need to add a new property:

public $return_data;

The constructor then sets the $return_data property to the text we want to display.

This gives a final pi.hello_world.php file of:

<?php 

class Hello_World {

    public $return_data;

    public function __construct()
    {
        $this->return_data = 'Hello, world';
    }

}

// End of file pi.hello_world.php

And we’re done!

Now, if we install the add-on and include the tag {exp:hello_world} in a template, it will display “Hello, world” in its place

This is a very simple plugin but it shows how easy it is to create an add-on. We’ll build on the basic ideas from this introduction to create more complex plugins.