Plugin coding guidelines

In addition to the Elgg Coding Standards, these are guidelines for creating plugins. Core plugins are being updated to this format and all plugin authors should follow these guidelines in their own plugins.

See also

Be sure to follow the Plugin skeleton for your plugin’s layout.

Warning

Don’t Modify Core

Use standardized routing with page handlers

  • Example: Bookmarks plugin

  • Page handlers should accept the following standard URLs:
    Purpose URL
    All page_handler/all
    User page_handler/owner/<username>
    User friends’ page_handler/friends/<username>
    Single entity page_handler/view/<guid>/<title>
    Add page_handler/add/<container_guid>
    Edit page_handler/edit/<guid>
    Group list page_handler/group/<guid>/owner

  • Include page handler scripts from the page handler. Almost every page handler should have a page handler script. (Example: bookmarks/all => mod/bookmarks/pages/bookmarks/all.php)

  • Call set_input() for entity guids in the page handler and use get_input() in the page handler scripts.

  • Call elgg_gatekeeper() and elgg_admin_gatekeeper() in the page handler function if required.

  • The group URL should use the pages/<handler>/owner.php script.

  • Page handlers should not contain HTML.

  • If upgrading a 1.7 plugin, update the URLs throughout the plugin. (Don’t forget to remove /pg/!)

Use standardized page handlers and scripts

  • Example: Bookmarks plugin
  • Store page handler scripts in mod/<plugin>/pages/<page_handler>/<page_name>
  • Use the content page layout in page handler scripts: $content = elgg_view_layout('content', $options);
  • Page handler scripts should not contain HTML
  • Call elgg_push_breadcrumb() in the page handler scripts.
  • No need to worry about setting the page owner if the URLs are in the standardized format
  • For group content, check the container_guid by using elgg_get_page_owner_entity()

The object/<subtype> view

  • Example: Bookmarks plugin

  • Make sure there are views for $vars[‘full’] == true and $vars[‘full’] == false

  • Check for the object in $vars[‘entity’] . Use elgg_instance_of() to make sure it’s the type entity you want. Return true to short circuit the view if the entity is missing or wrong.

  • Use the new list body and list metadata views to help format. You should use almost no markup in these views.

  • Update action structure - Example: Bookmarks plugin.

  • Namespace action files and action names (example: mod/blog/actions/blog/save.php => action/blog/save)

  • Use the following action URLs:
    Purpose URL
    Add action/plugin/save
    Edit action/plugin/save
    Delete action/plugin/delete

  • Make the delete action accept action/<handler>/delete?guid=<guid> so the metadata entity menu has the correct URL by default

  • If updating a 1.7 plugin, replace calls to functions deprecated in 1.7 because these will produce visible errors on every load in 1.8

Actions

Actions are transient states to perform an action such as updating the database or sending a notification to a user. Used correctly, actions are secure and prevent against CSRF and XSS attacks.

Note

As of Elgg 1.7 all actions require action tokens.

Action best practices

Never call an action directly by saying:

...href="/mod/mymod/actions/myaction.php"

This circumvents the security systems in Elgg.

There is no need to include the engine/start.php file in your actions. Actions should never be called directly, so the engine will be started automatically when called correctly.

Because actions are time-sensitive they are not suitable for links in emails or other delayed notifications. An example of this would be invitations to join a group. The clean way to create an invitation link is to create a page handler for invitations and email that link to the user. It is then the page handler’s responsibility to create the action links for a user to join or ignore the invitation request.

Directly calling a file

This is an easy one: Don’t do it. With the exception of 3rd party application integration, there is not a reason to directly call a file in mods directory.