Plugins Development

Plugins is another cool thing added alongside CodeIgniter. If you are not familiar with this term, you are invited to look for it on the internet. Major CMS has integrated plugins system (see WordPress plugins).

Creating Plugins

To create your first plugin, here are step you need to follow:

1. Create your plugin's folder within the content/plugins/ directory. The folder's name should be a slug representation of your plugin's name. For example, the Hello world example plugin's folder is name helloworld.
2. Create the main plugin's file (php file) with same name as the folder. For example, the Hello World plugin's main file is: content/plugins/helloworld.php.
3. Make sure to create the manifest.json (json) file within the plugin's folder. This file is required for the plugin to be recognized and listed. See below what this file should contain.

Here is an example of the manifest.json file of a plugin called The Title:

{
    "name": "Site name to title",
    "plugin_uri": "https://github.com/bkader/skeleton",
    "description": "This plugin adds website name to page title.",
    "version": "0.3.0",
    "license": "MIT",
    "license_uri": null,
    "author": "Kader Bouyakoub",
    "author_uri": "https://github.com/bkader",
    "author_email": "[email protected]",
    "tags": "csk, codeigniter, skeleton, plugin, title, ianhub, bkader",
    "translations": {
        "french": {
            "name": "Nom du site au titre",
            "description": "Ce plugin ajoute le nom du site aux titres des pages."
        },
        "arabic": {
            "name": "اسم الموقع إلى العنوان",
            "description": "يضيف هذا المكون الإضافي اسم موقع الويب إلى عناوين الصفحات."
        }
    }
}

You can provide languages files if needed. Simply add the language folder name and language index key to your manifest file, or use default ones, which are language for the folder and PLUGIN_FOLDER_NAME for language index. For custom ones, add inside your manifest file:

"language_folder": "i18n",
"language_index": "my-custom-index"

To retrieve your lines within your application, use the index like so:

echo line('line-to-retrieve', 'my-custom-index'); // Or plugins folder name as default.

Plugins Hooks

There are three (3) main actions you may use when creating your plugin (x is your plugin's slug):

1. plugin_install_x: triggered upon plugin's installation process.
2. plugin_activate_x: triggered upon plugin's activation.
3. plugin_deactivate_x: triggered upon plugin's deactivation.

Let's suppose I have a plugin called Hello World of which the folder is name helloworld. Here is how these actions can be used:

# Anonymous function:
add_action('plugin_install_helloworld', function() {
    // Do your magic.
});

# Defined function:
add_action('plugin_activate_helloworld', 'hello_world_activate');
if ( ! function_exists('hello_world_activate'))
{
    function hello_world_activate()
    {
        // Do your magic.
    }
}

# Within a class.
class Hello_world
{
    /**
     * Class constructor.
     */
    public function __construct()
    {
        add_action('plugin_install_helloworld',    array($this, 'install'));
        add_action('plugin_activate_helloworld',   array($this, 'activate'));
        add_action('plugin_deactivate_helloworld', array($this, 'deactivate'));
    }

    /**
     * Triggered upon plugin's installation.
     */
    public function install() { // DO YOUR MAGIC. }

    /**
     * Triggered upon plugin's activation.
     */
    public function activate() { // DO YOUR MAGIC. }

    /**
     * Triggered upon plugin's deactivation.
     */
    public function deactivate() { // DO YOUR MAGIC. }
}

# Then we initialize the class:
$hello_world = new Hello_world();

Plugins Settings

If you wish to add a settings page to your plugin, simply add the plugin_settings_x action, where x stands for your plugin's slug.

# same plugin: Hello World.
add_action('plugin_settings_helloworld', function() {
    # Output your settings page (HTML).
});

If you wish to use CodeIgniter featured (libraries, models ... etc) or provided skeleton libraries, make sure to call the $KB global variable within your functions or methods.

// This function uses CodeIgniter features:
function test()
{
    global $KB;

    # Load helpers, libraries and models:
    $KB->ci->load->helper('dummy');
    $KB->ci->load->library('form_validation'); # <- You can use form validation ;)
    $KB->ci->load->model('anything');
}

# To use the Skeleton libraries:
function test2()
{
    global $KB;

    # Entities, users, metadata ... etc:
    $KB->entities->get(1);
    $KB->users->get_by('username', 'bkader');
    $KB->metadata->get_meta(1, 'company', TRUE);
}

How To Use?

When developing your application, make sure to do actions and apply filters wherever your want themes/plugins to act.
Even if there are no filter or actions, just put them for later use.

Example

// Example of array I want themes/plugins to use:
$array = array('one', 'two', 'three');
$array = apply_filters('my_custom_filter', $array);

// Plugins/themes will simply need to add the filter:
add_filter('my_custom_filter', function($array) {
    // Add something or alter.
    array_push($array, 'four');
    return $array;
});

// The final result will be:
$array = array('one', 'two', 'three', 'four');

To learn more about this system, you can refer to WordPress documentation.