---
description: 
globs: 
alwaysApply: false
---
# Moodle Error Handling

## Purpose
Ensure consistent and proper error handling across all Moodle PHP code for better debugging and user experience.

## Instructions
When implementing error handling in Moodle PHP code, follow these practices:

1. **Use Moodle Exceptions**: Use `moodle_exception` and specific exception types
2. **Parameter Validation**: Use `required_param()`, `optional_param()` with proper validation
3. **Debugging**: Use `debugging()` for development, `error_log()` for critical errors
4. **User Feedback**: Provide meaningful error messages using language strings
5. **Graceful Degradation**: Handle errors gracefully without breaking the user experience
6. **Logging**: Use Moodle's logging system for important events and errors
7. **Context Information**: Include relevant context in error messages
8. **Error Recovery**: Implement recovery mechanisms where possible

## Examples

```php
<?php
// File: ./includes/error_handling_example.php

/**
 * Example of proper error handling in Moodle
 */
function process_user_action($userid, $action) {
    global $DB, $USER;
    
    try {
        // Parameter validation
        $userid = required_param('userid', PARAM_INT);
        $action = required_param('action', PARAM_ALPHA);
        
        // Validate user exists
        $user = $DB->get_record('user', ['id' => $userid], '*', MUST_EXIST);
        
        // Check permissions
        if (!has_capability('moodle/user:edit', context_user::instance($userid))) {
            throw new moodle_exception('nopermission', 'core');
        }
        
        // Perform action with error handling
        switch ($action) {
            case 'update':
                $result = update_user_profile($userid);
                break;
            case 'delete':
                $result = delete_user_data($userid);
                break;
            default:
                throw new moodle_exception('invalidaction', 'core');
        }
        
        // Log successful action
        \core\event\user_action_performed::create([
            'objectid' => $userid,
            'relateduserid' => $USER->id,
            'other' => ['action' => $action]
        ])->trigger();
        
        return $result;
        
    } catch (dml_exception $e) {
        // Database errors
        debugging('Database error: ' . $e->getMessage(), DEBUG_DEVELOPER);
        throw new moodle_exception('databaseerror', 'core');
        
    } catch (moodle_exception $e) {
        // Re-throw Moodle exceptions
        throw $e;
        
    } catch (Exception $e) {
        // Unexpected errors
        error_log('Unexpected error in process_user_action: ' . $e->getMessage());
        throw new moodle_exception('unknownerror', 'core');
    }
}

/**
 * Graceful error handling with user feedback
 */
function display_user_data($userid) {
    try {
        $userdata = get_user_data($userid);
        echo format_string($userdata->name);
        
    } catch (moodle_exception $e) {
        // Show user-friendly error
        echo html_writer::div(
            get_string('error_loading_user', 'core'),
            'alert alert-warning'
        );
        
        // Log detailed error for administrators
        debugging('Error loading user data: ' . $e->getMessage(), DEBUG_DEVELOPER);
    }
}
```

## Exceptions
- Critical system errors may require different handling approaches
- Third-party integrations may have specific error handling requirements