Plugins

Plugins must provide a manifest.xml file in the plugin root in order to be recognized by Elgg.

start.php

The start.php file bootstraps plugin by registering event listeners and plugin hooks.

It is advised that plugins return an instance of Closure from the start.php instead of placing registrations in the root of the file. This allows for consistency in Application bootstrapping, especially for testing purposes.

function my_plugin_does_something_else() {
    // Some procedural code that you want to run before any events are fired
}

function my_plugin_init() {
    // Your plugin's initialization logic
}

function my_plugin_rewrite_hook() {
    // Path rewrite hook
}

return function() {
    my_plugin_do_something_else();
    elgg_register_event_handler('init', 'system', 'my_plugin_init');
    elgg_register_plugin_hook_handler('route:rewrite', 'proifle', 'my_plugin_rewrite_hook');
}

elgg-plugin.php

elgg-plugin.php is a static plugin configuration file. It is read by Elgg to configure various services, and must return an array if present. It should not be included by plugins and is not guaranteed to run at any particular time. Besides magic constants like __DIR__, its return value should not change. The currently supported sections are:

  • bootstrap - defines a class used to bootstrap the plugin
  • entities - defines entity types and classes, and optionally registers them for search
  • actions - eliminates the need for calling elgg_register_action()
  • routes - eliminates the need for calling elgg_register_route()
  • settings - eliminates the need for setting default values on each call to elgg_get_plugin_setting()
  • user_settings - eliminates the need for setting default values on each call to elgg_get_plugin_user_setting()
  • views - allows plugins to alias vendor assets to a path within the Elgg’s view system
  • widgets - eliminates the need for calling elgg_register_widget_type()
return [
            // Bootstrap must implement \Elgg\PluginBootstrapInterface
            'bootstrap' => MyPluginBootstrap::class,

            'entities' => [
                    [
            // Register a new object subtype and tell Elgg to use a specific class to instantiate it
                            'type' => 'object',
                            'subtype' => 'my_object_subtype',
                            'class' => MyObjectClass::class,

                            // Register this subtype for search
                            'searchable' => true,
                    ],
            ],

            'actions' => [
                    // Registers an action
                    // By default, action is registered with 'logged_in' access
                    // By default, Elgg will look for file in plugin's actions/ directory: actions/my_plugin/action.php
                    'my_plugin/action/default' => [],

                    'my_plugin/action/custom_access' => [
                            'access' => 'public', // supports 'public', 'logged_in', 'admin'
                    ],

                    // you can use action controllers instead of action files by setting the controller parameters
                    // controller must be a callable that receives \Elgg\Request as the first and only argument
                    // in example below, MyActionController::__invoke(\Elgg\Request $request) will be called
                    'my_plugin/action/controller' => [
                            'controller' => MyActionController::class,
                    ],
            ],

            'routes' => [
                    // routes can be associated with resource views or controllers
                    'collection:object:my_object_subtype:all' => [
                            'path' => '/my_stuff/all',
                            'resource' => 'my_stuff/all', // view file is in resources/my_stuff/all
                    ],

                    // similar to actions, routes can be associated with a callable controller that receives an instance of \Elgg\Request
                    'collection:object:my_object_subtype:json' => [
                            'path' => '/my_stuff/json',
                            'controller' => JsonDumpController::class,
                    ],

                    // route definitions support other parameters, such as 'middleware', 'requirements', 'defaults'
                    // see elgg_register_route() for all options
            ],

            'widgets' => [
                    // register a new widget
                    // corresponds to a view in widgets/my_stuff/content
                    'my_stuff' => [
                            'description' => elgg_echo('widgets:my_stuff'),
                            'context' => ['profile', 'dashboard'],
                    ],
            ],

            'settings' => [
                    'plugin_setting_name' => 'plugin_setting_value',
            ],

            'user_settings' => [
                    'user_setting_name' => 'user_setting_value',
            ],

            // this is identical to using views.php in Elgg 2.x series
            'views' => [
                    'default' => [
                            'cool_lib/' => __DIR__ . '/vendors/cool_lib/dist/',
                    ],
            ],
    ];

elgg-services.php

Plugins can attach their services to Elgg’s public DI container by providing PHP-DI definitions in elgg-services.php in the root of the plugin directory.

This file must return an array of PHP-DI definitions. Services will by available via elgg().

Plugins can then use PHP-DI API to autowire and call the service:

See PHP-DI documentation for a comprehensive list of definition and invokation possibilities.

Syntax

Here’s a trivial example configuring view locations via the views key:

return [
        'views' => [
                'default' => [
                        'file/icon/' => __DIR__ . '/graphics/icons',
                ],
        ],
];

activate.php, deactivate.php

The activate.php and deactivate.php files contain procedural code that will run upon plugin activation and deactivation. Use these files to perform one-time events such as registering a persistent admin notice, registering subtypes, or performing garbage collection when deactivated.

manifest.xml

Elgg plugins are required to have a manifest.xml file in the root of a plugin.

The manifest.xml file includes information about the plugin itself, requirements to run the plugin, and optional information including where to display the plugin in the admin area and what APIs the plugin provides.

Syntax

The manifest file is a standard XML file in UTF-8. Everything is a child of the <plugin_manifest> element.

<?xml version="1.0" encoding="UTF-8" ?>
<plugin_manifest xmlns="http://www.elgg.org/plugin_manifest/1.8">

The manifest syntax is as follows:

<name>value</name>

Many elements can contain children attributes:

<parent_name>
        <child_name>value</child_name>
        <child_name_2>value_2</child_name_2>
</parent_name>

Required Elements

All plugins are required to define the following elements in their manifest files:

  • id - This has the name as the directory that the plugin uses.
  • name - The display name of the plugin.
  • author - The name of the author who wrote the plugin.
  • version - The version of the plugin.
  • description - A description of the what the plugin provides, its features, and other relevant information
  • requires - Each plugin must specify the release of Elgg it was developed for. See the plugin Dependencies page for more information.

Available Elements

In addition to the require elements above, the follow elements are available to use:

  • blurb - A short description of the plugin.
  • category - The category of the plugin. It is recommended to follow the Plugin coding guidelines and use one of the defined categories. There can be multiple entries.
  • conflicts - Specifies that the plugin conflicts with a certain system configuration.
  • copyright - The plugin’s copyright information.
  • license - The plugin’s license information.
  • provides - Specifies that this plugin provides the same functionality as another Elgg plugin or a PHP extension.
  • screenshot - Screenshots of the plugin. There can be multiple entries. See the advanced example for syntax.
  • suggests - Parallels the requires system, but doesn’t affect if the plugin can be enabled. Used to suggest other plugins that interact or build on the plugin.
  • website - A link to the website for the plugin.

Simple Example

This manifest file is the bare minimum a plugin must have.

<?xml version="1.0" encoding="UTF-8"?>
<plugin_manifest xmlns="http://www.elgg.org/plugin_manifest/1.8">
        <name>Example Manifest</name>
        <author>Elgg</author>
        <version>1.0</version>
        <description>This is a simple example of a manifest file. In this example, there are not screenshots, dependencies, or additional information about the plugin.</description>

        <requires>
                <type>elgg_release</type>
                <version>1.9</version>
        </requires>
</plugin_manifest>

Advanced example

This example uses all of the available elements:

<?xml version="1.0" encoding="UTF-8"?>
<plugin_manifest xmlns="http://www.elgg.org/plugin_manifest/1.8">
        <name>Example Manifest</name>
        <author>Brett Profitt</author>
        <version>1.0</version>
        <blurb>This is an example manifest file.</blurb>
        <description>This is a simple example of a manifest file. In this example, there are many options used, including screenshots, dependencies, and additional information about the plugin.</description>
        <website>http://www.elgg.org/</website>
        <copyright>(C) Brett Profitt 2014</copyright>
        <license>GNU Public License version 2</license>

        <category>3rd_party_integration</category>

        <requires>
                <type>elgg_release</type>
                <version>1.9.1</version>
        </requires>

        <!-- The path is relative to the plugin's root. -->
        <screenshot>
                <description>Elgg profile.</description>
                <path>screenshots/profile.png</path>
        </screenshot>

        <provides>
                <type>plugin</type>
                <name>example_plugin</name>
                <version>1.5</version>
        </provides>

        <suggests>
                <type>plugin</type>
                <name>twitter</name>
                <version>1.0</version>
        </suggests>
</plugin_manifest>

composer.json

Since Elgg supports being installed as a Composer dependency, having your plugins also support Composer makes for easier installation by site administrators. In order to make your plugin compatible with Composer you need to at least have a composer.json file in the root of your plugin.

Here is an example of a composer.json file:

{
        "name": "company/example_plugin",
        "description": "Some description of the plugin",
        "type": "elgg-plugin",
        "keywords": ["elgg", "plugin"],
        "license": "GPL-2.0-only",
        "support": {
                "source": "URL to your code repository",
                "issues": "URL to your issue tracker"
        },
        "require": {
                "composer/installers": "^1.0.8"
        },
        "conflict": {
                "elgg/elgg": "<3.0"
        }
}

Read more about the composer.json format on the Composer website.

Important parts in the composer.json file are:

  • name: the name of your plugin, keep this inline with the name of your plugin folder to ensure correct installation
  • type: this will tell Composer where to install your plugin, ALWAYS keep this as elgg-plugin
  • require: the composer/installers requirement is to make sure Composer knows where to install your plugin

As a suggestion, include a conflict rule with any Elgg version below your mininal required version, this will help prevent the accidental installation of your plugin on an incompatible Elgg version.

After adding a composer.json file to your plugin project, you need to register your project on Packagist in order for other people to be able to install your plugin.

Tests

It’s encouraged to create PHPUnit test for your plugin. All tests should be located in tests/phpunit/unit for unit tests and tests/phpunit/integration for integration tests.

An easy example of adding test is the ViewStackTest, this will test that the views in your plugin are registered correctly and have no syntax errors. To add this test create a file ViewStackTest.php in the folder tests/phpunit/unit/<YourNameSpace>/<YourPluginName>/ with the content:

namespace <YourNameSpace>\<YourPluginName>;

/**
 * @group ViewsService
 */
class ViewStackTest extends \Elgg\Plugins\ViewStackTest {

}

Note

If you wish to see a better example, look in any of the Elgg core plugins.

See also

Writing tests