Moodle External API Development
This skill guides you through creating custom external web service APIs for Moodle LMS, following Moodle's external API framework and coding standards.
When to Use This Skill Creating custom web services for Moodle plugins Implementing REST/AJAX endpoints for course management Building APIs for quiz operations, user tracking, or reporting Exposing Moodle functionality to external applications Developing mobile app backends using Moodle Core Architecture Pattern
Moodle external APIs follow a strict three-method pattern:
execute_parameters() - Defines input parameter structure execute() - Contains business logic execute_returns() - Defines return structure Step-by-Step Implementation Step 1: Create the External API Class File
Location: /local/yourplugin/classes/external/your_api_name.php
libdir/externallib.php"); use external_api; use external_function_parameters; use external_single_structure; use external_value; class your_api_name extends external_api { // Three required methods will go here } Key Points: Class must extend external_api Namespace follows: local_pluginname\external or mod_modname\external Include the security check: defined('MOODLE_INTERNAL') || die(); Require externallib.php for base classes Step 2: Define Input Parameters public static function execute_parameters() { return new external_function_parameters([ 'userid' => new external_value(PARAM_INT, 'User ID', VALUE_REQUIRED), 'courseid' => new external_value(PARAM_INT, 'Course ID', VALUE_REQUIRED), 'options' => new external_single_structure([ 'includedetails' => new external_value(PARAM_BOOL, 'Include details', VALUE_DEFAULT, false), 'limit' => new external_value(PARAM_INT, 'Result limit', VALUE_DEFAULT, 10) ], 'Options', VALUE_OPTIONAL) ]); } Common Parameter Types: PARAM_INT - Integers PARAM_TEXT - Plain text (HTML stripped) PARAM_RAW - Raw text (no cleaning) PARAM_BOOL - Boolean values PARAM_FLOAT - Floating point numbers PARAM_ALPHANUMEXT - Alphanumeric with extended chars Structures: external_value - Single value external_single_structure - Object with named fields external_multiple_structure - Array of items Value Flags: VALUE_REQUIRED - Parameter must be provided VALUE_OPTIONAL - Parameter is optional VALUE_DEFAULT, defaultvalue - Optional with default Step 3: Implement Business Logic public static function execute($userid, $courseid, $options = []) { global $DB, $USER; // 1. Validate parameters $params = self::validate_parameters(self::execute_parameters(), [ 'userid' => $userid, 'courseid' => $courseid, 'options' => $options ]); // 2. Check permissions/capabilities $context = \context_course::instance($params['courseid']); self::validate_context($context); require_capability('moodle/course:view', $context); // 3. Verify user access if ($params['userid'] != $USER->id) { require_capability('moodle/course:viewhiddenactivities', $context); } // 4. Database operations $sql = "SELECT id, name, timecreated FROM {your_table} WHERE userid = :userid AND courseid = :courseid LIMIT :limit"; $records = $DB->get_records_sql($sql, [ 'userid' => $params['userid'], 'courseid' => $params['courseid'], 'limit' => $params['options']['limit'] ]); // 5. Process and return data $results = []; foreach ($records as $record) { $results[] = [ 'id' => $record->id, 'name' => $record->name, 'timestamp' => $record->timecreated ]; } return [ 'items' => $results, 'count' => count($results) ]; } Critical Steps: Always validate parameters using validate_parameters() Check context using validate_context() Verify capabilities using require_capability() Use parameterized queries to prevent SQL injection Return structured data matching return definition Step 4: Define Return Structure public static function execute_returns() { return new external_single_structure([ 'items' => new external_multiple_structure( new external_single_structure([ 'id' => new external_value(PARAM_INT, 'Item ID'), 'name' => new external_value(PARAM_TEXT, 'Item name'), 'timestamp' => new external_value(PARAM_INT, 'Creation time') ]) ), 'count' => new external_value(PARAM_INT, 'Total items') ]); } Return Structure Rules: Must match exactly what execute() returns Use appropriate parameter types Document each field with description Nested structures allowed Step 5: Register the Service Location: /local/yourplugin/db/services.php [ 'classname' => 'local_yourplugin\external\your_api_name', 'methodname' => 'execute', 'classpath' => 'local/yourplugin/classes/external/your_api_name.php', 'description' => 'Brief description of what this API does', 'type' => 'read', // or 'write' 'ajax' => true, 'capabilities'=> 'moodle/course:view', // comma-separated if multiple 'services' => [MOODLE_OFFICIAL_MOBILE_SERVICE] // Optional ], ]; $services = [ 'Your Plugin Web Service' => [ 'functions' => [ 'local_yourplugin_your_api_name' ], 'restrictedusers' => 0, 'enabled' => 1 ] ]; Service Registration Keys: classname - Full namespaced class name methodname - Always 'execute' type - 'read' (SELECT) or 'write' (INSERT/UPDATE/DELETE) ajax - Set true for AJAX/REST access capabilities - Required Moodle capabilities services - Optional service bundles Step 6: Implement Error Handling & Logging private static function log_debug($message) { global $CFG; $logdir = $CFG->dataroot . '/local_yourplugin'; if (!file_exists($logdir)) { mkdir($logdir, 0777, true); } $debuglog = $logdir . '/api_debug.log'; $timestamp = date('Y-m-d H:i:s'); file_put_contents($debuglog, "[$timestamp] $message\n", FILE_APPEND | LOCK_EX); } public static function execute($userid, $courseid) { global $DB; try { self::log_debug("API called: userid=$userid, courseid=$courseid"); // Validate parameters $params = self::validate_parameters(self::execute_parameters(), [ 'userid' => $userid, 'courseid' => $courseid ]); // Your logic here self::log_debug("API completed successfully"); return $result; } catch (\invalid_parameter_exception $e) { self::log_debug("Parameter validation failed: " . $e->getMessage()); throw $e; } catch (\moodle_exception $e) { self::log_debug("Moodle exception: " . $e->getMessage()); throw $e; } catch (\Exception $e) { // Log detailed error info $lastsql = method_exists($DB, 'get_last_sql') ? $DB->get_last_sql() : '[N/A]'; self::log_debug("Fatal error: " . $e->getMessage()); self::log_debug("Last SQL: " . $lastsql); self::log_debug("Stack trace: " . $e->getTraceAsString()); throw $e; } } Error Handling Best Practices: Wrap logic in try-catch blocks Log errors with timestamps and context Capture SQL queries on database errors Preserve stack traces for debugging Re-throw exceptions after logging Advanced Patterns Complex Database Operations // Transaction example $transaction = $DB->start_delegated_transaction(); try { // Insert record $recordid = $DB->insert_record('your_table', $dataobject); // Update related records $DB->set_field('another_table', 'status', 1, ['recordid' => $recordid]); // Commit transaction $transaction->allow_commit(); } catch (\Exception $e) { $transaction->rollback($e); throw $e; } Working with Course Modules // Create course module $moduleid = $DB->get_field('modules', 'id', ['name' => 'quiz'], MUST_EXIST); $cm = new \stdClass(); $cm->course = $courseid; $cm->module = $moduleid; $cm->instance = 0; // Will be updated after activity creation $cm->visible = 1; $cm->groupmode = 0; $cmid = add_course_module($cm); // Create activity instance (e.g., quiz) $quiz = new \stdClass(); $quiz->course = $courseid; $quiz->name = 'My Quiz'; $quiz->coursemodule = $cmid; // ... other quiz fields ... $quizid = quiz_add_instance($quiz, null); // Update course module with instance ID $DB->set_field('course_modules', 'instance', $quizid, ['id' => $cmid]); course_add_cm_to_section($courseid, $cmid, 0); Access Restrictions (Groups/Availability) // Restrict activity to specific user via group $groupname = 'activity_' . $activityid . '_user_' . $userid; // Create or get group if (!$groupid = $DB->get_field('groups', 'id', ['courseid' => $courseid, 'name' => $groupname])) { $groupdata = (object)[ 'courseid' => $courseid, 'name' => $groupname, 'timecreated' => time(), 'timemodified' => time() ]; $groupid = $DB->insert_record('groups', $groupdata); } // Add user to group if (!$DB->record_exists('groups_members', ['groupid' => $groupid, 'userid' => $userid])) { $DB->insert_record('groups_members', (object)[ 'groupid' => $groupid, 'userid' => $userid, 'timeadded' => time() ]); } // Set availability condition $restriction = [ 'op' => '&', 'show' => false, 'c' => [ [ 'type' => 'group', 'id' => $groupid ] ], 'showc' => [false] ]; $DB->set_field('course_modules', 'availability', json_encode($restriction), ['id' => $cmid]); Random Question Selection with Tags private static function get_random_questions($categoryid, $tagname, $limit) { global $DB; $sql = "SELECT q.id FROM {question} q INNER JOIN {question_versions} qv ON qv.questionid = q.id INNER JOIN {question_bank_entries} qbe ON qbe.id = qv.questionbankentryid INNER JOIN {question_categories} qc ON qc.id = qbe.questioncategoryid JOIN {tag_instance} ti ON ti.itemid = q.id JOIN {tag} t ON t.id = ti.tagid WHERE LOWER(t.name) = :tagname AND qc.id = :categoryid AND ti.itemtype = 'question' AND q.qtype = 'multichoice'"; $qids = $DB->get_fieldset_sql($sql, [ 'categoryid' => $categoryid, 'tagname' => strtolower($tagname) ]); shuffle($qids); return array_slice($qids, 0, $limit); } Testing Your API 1. Via Moodle Web Services Test Client Enable web services: Site administration > Advanced features Enable REST protocol: Site administration > Plugins > Web services > Manage protocols Create service: Site administration > Server > Web services > External services Test function: Site administration > Development > Web service test client 2. Via curl # Get token first curl -X POST "https://yourmoodle.com/login/token.php" \ -d "username=admin" \ -d "password=yourpassword" \ -d "service=moodle_mobile_app" # Call your API curl -X POST "https://yourmoodle.com/webservice/rest/server.php" \ -d "wstoken=YOUR_TOKEN" \ -d "wsfunction=local_yourplugin_your_api_name" \ -d "moodlewsrestformat=json" \ -d "userid=2" \ -d "courseid=3" 3. Via JavaScript (AJAX) require(['core/ajax'], function(ajax) { var promises = ajax.call([{ methodname: 'local_yourplugin_your_api_name', args: { userid: 2, courseid: 3 } }]); promises[0].done(function(response) { console.log('Success:', response); }).fail(function(error) { console.error('Error:', error); }); }); Common Pitfalls & Solutions 1. "Function not found" Error Solution: Purge caches: Site administration > Development > Purge all caches Verify function name in services.php matches exactly Check namespace and class name are correct 2. "Invalid parameter value detected" Solution: Ensure parameter types match between definition and usage Check required vs optional parameters Validate nested structure definitions 3. SQL Injection Vulnerabilities Solution: Always use placeholder parameters (:paramname) Never concatenate user input into SQL strings Use Moodle's database methods: get_record(), get_records(), etc. 4. Permission Denied Errors Solution: Call self::validate_context($context) early in execute() Check required capabilities match user's permissions Verify user has role assignments in the context 5. Transaction Deadlocks Solution: Keep transactions short Always commit or rollback in finally blocks Avoid nested transactions Debugging Checklist Check Moodle debug mode: Site administration > Development > Debugging Review web services logs: Site administration > Reports > Logs Check custom log files in $CFG->dataroot/local_yourplugin/ Verify database queries using $DB->set_debug(true) Test with admin user to rule out permission issues Clear browser cache and Moodle caches Check PHP error logs on server Plugin Structure Checklist local/yourplugin/ ├── version.php # Plugin version and metadata ├── db/ │ ├── services.php # External service definitions │ └── access.php # Capability definitions (optional) ├── classes/ │ └── external/ │ ├── your_api_name.php # External API implementation │ └── another_api.php # Additional APIs ├── lang/ │ └── en/ │ └── local_yourplugin.php # Language strings └── tests/ └── external_test.php # Unit tests (optional but recommended) Examples from Real Implementation Simple Read API (Get Quiz Attempts) libdir/externallib.php"); use external_api; use external_function_parameters; use external_single_structure; use external_value; class get_quiz_attempts extends external_api { public static function execute_parameters() { return new external_function_parameters([ 'userid' => new external_value(PARAM_INT, 'User ID'), 'courseid' => new external_value(PARAM_INT, 'Course ID') ]); } public static function execute($userid, $courseid) { global $DB; self::validate_parameters(self::execute_parameters(), [ 'userid' => $userid, 'courseid' => $courseid ]); $sql = "SELECT COUNT(*) AS quiz_attempts FROM {quiz_attempts} qa JOIN {quiz} q ON qa.quiz = q.id WHERE qa.userid = :userid AND q.course = :courseid"; $attempts = $DB->get_field_sql($sql, [ 'userid' => $userid, 'courseid' => $courseid ]); return ['quiz_attempts' => (int)$attempts]; } public static function execute_returns() { return new external_single_structure([ 'quiz_attempts' => new external_value(PARAM_INT, 'Total number of quiz attempts') ]); } } Complex Write API (Create Quiz from Categories) See attached create_quiz_from_categories.php for a comprehensive example including: Multiple database insertions Course module creation Quiz instance configuration Random question selection with tags Group-based access restrictions Extensive error logging Transaction management Quick Reference: Common Moodle Tables Table Purpose {user} User accounts {course} Courses {course_modules} Activity instances in courses {modules} Available activity types (quiz, forum, etc.) {quiz} Quiz configurations {quiz_attempts} Quiz attempt records {question} Question bank {question_categories} Question categories {grade_items} Gradebook items {grade_grades} Student grades {groups} Course groups {groups_members} Group memberships {logstore_standard_log} Activity logs Additional Resources Moodle External API Documentation Moodle Coding Style Moodle Database API Web Services API Documentation Guidelines Always validate input parameters using validate_parameters() Check user context and capabilities before operations Use parameterized SQL queries (never string concatenation) Implement comprehensive error handling and logging Follow Moodle naming conventions (lowercase, underscores) Document all parameters and return values clearly Test with different user roles and permissions Consider transaction safety for write operations Purge caches after service registration changes Keep API methods focused and single-purpose ?>