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Extension Structure

Extension Files

The civix command line tool will generate the following structure for you:

  • info.xml is a manifest that describes your extension – the name, license, version number, etc. You should edit most information in this file. The information contained in this file will also be used if published on
  • myextension.php stores source code for all your hooks. It includes a few default hook implementations which will make development easier. You can add and remove hooks as you wish. (Note: This file name is different in each module – it is based the module's short-name.)
  • myextension.civix.php contains auto-generated helper functions. These deal with common problems like registering your module in the template include-path. civix may automatically overwrite this file, so generally do not edit it.

Extension Directory Structure

In addition, civix creates some empty directories. These directories are reminiscent of the directory structure in CiviCRM core:

  • CRM/Myextension/ stores PHP class files. Classes in this folder should be prefixed with "CRM_Myextension_".
  • templates/ stores Smarty templates.
  • xml/ stores XML configuration files (such as URL routes and schema xml).
  • build/ stores exportable .zip files.

When adding files into these directories it is advisable to follow similar patterns to that in CiviCRM Core e.g. BAO files should go in "CRM\Myextension\BAO\", likewise with Form and Page. This ensures that for developers that seek to modify or improve the extension files can be found in standard locations.

The Big E

There are many times when you need to reference something from the extension -- e.g. its name, its file-path, or its translated messages.

For example, this code displays a translated message (using the translation data for this extension):

if ($welcoming) {
  CRM_Core_Session::setStatus(ts('Hello world!', array(
    'domain' => 'org.civicrm.myextension',
} else {
  CRM_Core_Session::setStatus(ts('Goodbye cruel world!', array(
    'domain' => 'org.civicrm.myextension',

Repeatedly entering the name of the extension is a bit tiresome.

For code generated by civix v17.08.0+ (or suitably upgraded), civix includes the E helper which provides easier access:

use CRM_Mymodule_ExtensionUtil as E;

if ($welcoming) {
  CRM_Core_Session::setStatus(E::ts('Hello world!'));
} else {
  CRM_Core_Session::setStatus(E::ts('Goodbye cruel world!'));

Note that E is an alias. It stands for "extension" -- as in "the current extension that I'm writing". It's a very thin class that provides small helpers for looking up your extension's resources, e.g.

  • E::ts($text) -- Translate a string (using the extensions' translation file)
  • E::path($file) -- Get the path to a resource file (within this extension)
  • E::url($file) -- Get the URL to a resource file (within this extension)
  • E::findClass($suffix) -- Get the full name of a class (within this extension)
  • E::LONG_NAME -- The full length key for this extension (eg org.example.myextension)
  • E::SHORT_NAME -- The abbreviated key for this extension (eg myextension)