moodle-plugin-development

Moodle Plugin Development

Overview

Moodle plugins follow strict frankenstyle naming and a fixed file layout. Every plugin lives under a type-specific directory (local/, mod/, blocks/, course/format/, theme/, auth/, enrol/, report/, question/type/, filter/, repository/, etc.) and is identified by <type>_<name> (e.g., local_school, mod_quiz, format_schoolgram).

Core principle: Moodle code must declare defined('MOODLE_INTERNAL') || die(); at top of every PHP file (except classes under classes/ autoloaded via PSR-4), use $DB for all DB access, use get_string() for user-facing text, and bump version.php for any DB or capability change.

When to Use

• Creating new plugin under local/, mod/, blocks/, course/format/, theme/, etc.
• Adding/modifying DB tables → db/install.xml + db/upgrade.php
• Adding capabilities → db/access.php
• Adding web services / external functions → db/services.php + classes/external/
• Adding scheduled tasks → db/tasks.php + classes/task/
• Adding events / observers → db/events.php + classes/event/
• Adding admin settings page → settings.php
• Translating strings → lang/<lang>/<component>.php
• Reviewing PR for Moodle coding-style compliance
• Bumping version.php after schema/capability change

Skip when: working purely on frontend AMD modules without backend changes, or non-Moodle PHP code.

Plugin Skeleton

Minimum files for a local_<name> plugin:

local/<name>/
  version.php                    # required: component, version, requires, maturity
  lang/en/local_<name>.php       # required: 'pluginname' string
  lib.php                        # optional: hooks (extend_navigation, pluginfile, etc.)
  settings.php                   # optional: admin settings page
  db/
    install.xml                  # DB schema (edit via /admin/tool/xmldb/)
    upgrade.php                  # versioned upgrade steps
    access.php                   # capabilities
    services.php                 # web service definitions
    tasks.php                    # scheduled tasks
    events.php                   # event observers
    caches.php                   # cache definitions
  classes/                       # PSR-4: \local_<name>\foo\bar -> classes/foo/bar.php
    external/                    # external (web service) functions
    task/                        # scheduled task classes
    event/                       # custom events
    privacy/provider.php         # GDPR provider (REQUIRED)
  templates/                     # Mustache templates
  amd/src/                       # ES modules (built via grunt -> amd/build/)
  tests/                         # PHPUnit + Behat

version.php Template

<?php
defined('MOODLE_INTERNAL') || die();

$plugin->component = 'local_example';      // frankenstyle, must match dir
$plugin->version   = 2026042500;           // YYYYMMDDXX, bump on any db/capability change
$plugin->requires  = 2024100700;           // min Moodle version (4.5 LTS); use 2025041400 for 5.0+, 2025100600 for 5.1+, 2026042000 for 5.2+
$plugin->release   = '1.0.0';
$plugin->maturity  = MATURITY_STABLE;      // ALPHA | BETA | RC | STABLE
$plugin->dependencies = ['mod_quiz' => 2024100700];  // optional

db/install.xml + upgrade.php

• Edit install.xml via Moodle XMLDB editor (Site admin -> Development -> XMLDB editor) — never hand-edit.
• Every schema change requires:
  1. Bump $plugin->version in version.php
  2. Add upgrade step in db/upgrade.php keyed on old version:

function xmldb_local_example_upgrade($oldversion) {
    global $DB;
    $dbman = $DB->get_manager();

    if ($oldversion < 2026042500) {
        $table = new xmldb_table('local_example_items');
        $field = new xmldb_field('status', XMLDB_TYPE_INTEGER, '4', null,
            XMLDB_NOTNULL, null, '0', 'name');
        if (!$dbman->field_exists($table, $field)) {
            $dbman->add_field($table, $field);
        }
        upgrade_plugin_savepoint(true, 2026042500, 'local', 'example');
    }
    return true;
}

db/access.php Capabilities

$capabilities = [
    'local/example:view' => [
        'captype'      => 'read',
        'contextlevel' => CONTEXT_SYSTEM,
        'archetypes'   => [
            'user'           => CAP_ALLOW,
            'editingteacher' => CAP_ALLOW,
        ],
    ],
];

Runtime check: require_capability('local/example:view', $context); or has_capability(...).

db/services.php (Web Services / AJAX)

$functions = [
    'local_example_get_items' => [
        'classname'    => 'local_example\external\get_items',
        'methodname'   => 'execute',
        'description'  => 'Return items',
        'type'         => 'read',
        'ajax'         => true,
        'capabilities' => 'local/example:view',
    ],
];

External class extends \core_external\external_api (Moodle 4.2+; older = external_api) and defines execute_parameters(), execute(), execute_returns().

Lang Strings

lang/en/local_example.php:

$string['pluginname']    = 'Example';
$string['example:view']  = 'View example';        // capability strings: <plugin>:<cap>
$string['greeting']      = 'Hello, {$a->name}';   // placeholders

Use: get_string('greeting', 'local_example', ['name' => $user->firstname]);

DB Access — Always $DB

global $DB;
$DB->get_record('local_example_items', ['id' => $id], '*', MUST_EXIST);
$DB->get_records_sql('SELECT * FROM {local_example_items} WHERE status = ?', [1]);
$DB->insert_record('local_example_items', $obj);
$DB->update_record('local_example_items', $obj);
$DB->delete_records('local_example_items', ['id' => $id]);

Never mysqli_* / PDO. Always use {tablename} placeholder (Moodle prefixes). Always bind params, never concatenate.

Hooks via lib.php

Common Moodle callbacks (function name = <component>_<hookname>):

• local_example_extend_navigation(global_navigation $nav) — add nav nodes
• local_example_before_http_headers() — runs before headers
• local_example_extend_settings_navigation($settingsnav, $context)
• local_example_pluginfile($course, $cm, $context, $filearea, $args, $forcedl, $options) — serve file area

Moodle 4.4+: prefer the new hooks API (\core\hook\manager) over magic callbacks where available.

Output — Renderers + Templates

• HTML via $OUTPUT->render_from_template('local_example/foo', $data) (Mustache: templates/foo.mustache)
• Custom renderer: classes/output/renderer.php extends plugin_renderer_base
• Never echo raw HTML in business logic; always go through renderer or template

Privacy (GDPR) — Required

Every plugin must declare privacy. Minimum (no user data stored):

// classes/privacy/provider.php
namespace local_example\privacy;
defined('MOODLE_INTERNAL') || die();
class provider implements \core_privacy\local\metadata\null_provider {
    public static function get_reason(): string {
        return 'privacy:metadata';
    }
}

If plugin stores user data, implement \core_privacy\local\request\plugin\provider and define get_metadata, export_user_data, delete_data_for_user_in_context, delete_data_for_users, get_contexts_for_userid, get_users_in_context.

Quick Reference

Task	File	Bump version?
Add DB table/field	db/install.xml + db/upgrade.php	Yes
Add capability	db/access.php + lang string	Yes
Add web service fn	db/services.php + classes/external/	Yes
Add scheduled task	db/tasks.php + classes/task/	Yes
Add event observer	db/events.php	Yes
Add cache definition	db/caches.php	Yes
Add string	lang/en/<component>.php	No
Add settings	settings.php	No
Add template	templates/*.mustache	No
Add renderer	classes/output/renderer.php	No

Coding Standards

• 4-space indent, no tabs
• Opening <?php on line 1, no closing ?> at end of pure PHP files
• defined('MOODLE_INTERNAL') || die(); immediately after license block (skip in classes/ PSR-4 files)
• snake_case for functions/vars, PascalCase for classes
• Run vendor/bin/phpcs --standard=moodle <path> before commit (local_codechecker plugin or moodle-cs ruleset)
• All user-facing strings via get_string(), never hard-coded English
• GPL-3.0-or-later license header on every PHP file

Common Mistakes

Mistake	Fix
Hand-editing install.xml	Use XMLDB editor at /admin/tool/xmldb/
Forgetting to bump version.php after schema change	Bump + add upgrade.php step + upgrade_plugin_savepoint
Using raw SQL with {} quoting wrong	Use {tablename} and ? / named params, never string concat
MOODLE_INTERNAL check inside classes/ PSR-4 file	Remove — autoloaded files don't need it
Storing user data without privacy provider	Implement \core_privacy\local\request\plugin\provider
Hard-coded English strings in PHP/Mustache	Move to lang/en/<component>.php + get_string / {{#str}}
Forgetting require_capability() on entry points	Always require_login() + capability check early
Not purging caches after version.php bump	php admin/cli/upgrade.php or Site admin -> Purge caches
Direct $_GET/$_POST access	Use required_param() / optional_param() with type
Missing sesskey() check on state-changing requests	Call require_sesskey() on POST handlers

Plugin Type Cheatsheet

Type	Dir	Frankenstyle	Extra required files
Local	local/<name>	local_<name>	none beyond skeleton
Activity module	mod/<name>	mod_<name>	mod_form.php, view.php, lib.php w/ <name>_add_instance etc.
Block	blocks/<name>	block_<name>	block_<name>.php extends block_base
Course format	course/format/<name>	format_<name>	format.php, lib.php extends core_courseformat\base
Theme	theme/<name>	theme_<name>	config.php, scss/, layout/
Auth	auth/<name>	auth_<name>	auth.php extends auth_plugin_base
Enrol	enrol/<name>	enrol_<name>	lib.php extends enrol_plugin
Question type	question/type/<name>	qtype_<name>	questiontype.php, question.php, renderer.php
Filter	filter/<name>	filter_<name>	filter.php extends moodle_text_filter
Repository	repository/<name>	repository_<name>	lib.php extends repository

Security Checklist

• require_login() (and require_capability()) at top of every entry script
• require_sesskey() on every state-changing POST
• required_param($name, PARAM_INT) / optional_param(...) — never raw $_REQUEST
• Use $DB->... with placeholders — no SQL concat
• Escape output: s(), format_string(), format_text()
• File serving via pluginfile.php + <component>_pluginfile() callback, never direct path

CLI Helpers

php admin/cli/upgrade.php --non-interactive    # apply pending upgrades
php admin/cli/purge_caches.php                  # clear all caches
php admin/tool/behat/cli/init.php               # init behat tests
vendor/bin/phpunit --testsuite local_example_testsuite
vendor/bin/phpcs --standard=moodle local/example

Testing

• PHPUnit: tests/<thing>_test.php extending advanced_testcase, use $this->resetAfterTest(), generators via self::getDataGenerator()->get_plugin_generator('local_example')
• Behat: tests/behat/*.feature with @local_example tag, step definitions in tests/behat/behat_local_example.php

References

• Moodle Dev Docs: https://moodledev.io
• Plugin types: https://moodledev.io/docs/apis/plugintypes
• Coding style: https://moodledev.io/general/development/policies/codingstyle
• XMLDB: https://moodledev.io/docs/apis/core/dml/xmldb
• Privacy API: https://moodledev.io/docs/apis/subsystems/privacy
• Hooks API (4.4+): https://moodledev.io/docs/apis/core/hooks