Add PHP skill support

.semgrepignore

@@ -13,3 +13,7 @@
 basics/react-native/android/app/src/main/AndroidManifest.xml
 basics/expo/android/app/src/main/AndroidManifest.xml
 basics/android/app/src/main/AndroidManifest.xml
+
+# Markdown audit reference contains HogQL examples with PostHog $host event property.
+# Semgrep's nginx host-header rule misidentifies this docs-only SQL as nginx config.
+transformation-config/skills/audit-events/references/3-events-optimize.md

basics/php/.env.example

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+# PostHog configuration
+POSTHOG_API_KEY=phc_your_api_key_here
+POSTHOG_HOST=https://us.i.posthog.com

basics/php/.gitignore

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+vendor/
+.env
+composer.lock
+.todo_app.json

basics/php/README.md

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+# PostHog PHP Example - CLI Todo App
+
+A simple command-line todo application built with plain PHP (no framework) demonstrating PostHog integration for CLIs, scripts, data pipelines, and non-web PHP applications.
+
+## Purpose
+
+This example serves as:
+- **Verification** that the context-mill wizard works for plain PHP projects
+- **Reference implementation** of PostHog best practices for non-framework PHP code
+- **Working example** you can run and modify
+
+## Features Demonstrated
+
+- **SDK initialization** - Uses `PostHog::init(...)` once with environment-based configuration
+- **Event tracking** - Captures user actions with `distinctId` and properties
+- **User identification** - Associates properties with users via `PostHog::identify(...)`
+- **Error tracking** - Enables automatic PHP error tracking and manually captures handled exceptions
+- **Proper flushing** - Calls `PostHog::flush()` before CLI exit
+
+## Quick Start
+
+### 1. Install Dependencies
+
+```bash
+composer install
+```
+
+### 2. Configure PostHog
+
+```bash
+# Copy environment template
+cp .env.example .env
+
+# Edit .env and add your PostHog API key
+# POSTHOG_API_KEY=phc_your_api_key_here
+# POSTHOG_HOST=https://us.i.posthog.com
+```
+
+### 3. Run the App
+
+```bash
+# Add a todo
+php todo.php add "Buy groceries"
+
+# List all todos
+php todo.php list
+
+# Complete a todo
+php todo.php complete 1
+
+# Delete a todo
+php todo.php delete 1
+
+# Show statistics
+php todo.php stats
+```
+
+## What Gets Tracked
+
+The app tracks these events in PostHog:
+
+| Event | Properties | Purpose |
+|-------|-----------|---------|
+| `todo_added` | `todo_id`, `todo_length`, `total_todos` | When user adds a new todo |
+| `todos_viewed` | `total_todos`, `completed_todos` | When user lists todos |
+| `todo_completed` | `todo_id`, `time_to_complete_hours` | When user completes a todo |
+| `todo_deleted` | `todo_id`, `was_completed` | When user deletes a todo |
+| `stats_viewed` | `total_todos`, `completed_todos`, `pending_todos` | When user views stats |
+| `$exception` | exception details and command context | When handled errors occur |
+
+## Code Structure
+
+```
+basics/php/
+├── todo.php             # Main CLI application
+├── composer.json        # PHP dependencies
+├── .env.example         # Environment variable template
+├── .gitignore           # Git ignore rules
+└── README.md            # This file
+```
+
+## Key Implementation Patterns
+
+### 1. Initialize Once
+
+```php
+PostHog::init($apiKey, [
+    'host' => $host,
+    'error_tracking' => [
+        'enabled' => true,
+    ],
+]);
+```
+
+### 2. Event Tracking Pattern
+
+```php
+PostHog::capture([
+    'distinctId' => 'user_123',
+    'event' => 'event_name',
+    'properties' => ['key' => 'value'],
+]);
+```
+
+### 3. Identifying Users
+
+```php
+PostHog::identify([
+    'distinctId' => 'user_123',
+    'properties' => ['app_language' => 'php'],
+]);
+```
+
+### 4. Exception Tracking
+
+```php
+try {
+    riskyOperation();
+} catch (Throwable $e) {
+    PostHog::captureException($e, 'user_123', [
+        'command' => 'example_command',
+    ]);
+}
+```
+
+### 5. Flush Before CLI Exit
+
+```php
+PostHog::flush();
+```
+
+## Running Without PostHog
+
+The app works fine without PostHog configured - it simply won't track analytics. You'll see a warning message but the app continues to function normally.
+
+## Next Steps
+
+- Modify `todo.php` to experiment with PostHog tracking
+- Add new commands and track their usage
+- Explore feature flags: `PostHog::isFeatureEnabled('flag-name', 'user_id')`
+- Check your PostHog dashboard to see tracked events
+
+## Learn More
+
+- [PostHog PHP SDK Documentation](https://posthog.com/docs/libraries/php)
+- [PostHog PHP Error Tracking](https://posthog.com/docs/error-tracking/installation/php)
+- [PostHog Product Analytics PHP installation](https://posthog.com/docs/product-analytics/installation/php)

basics/php/composer.json

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+{
+  "name": "posthog/context-mill-php-example",
+  "description": "Plain PHP CLI todo app demonstrating PostHog integration",
+  "type": "project",
+  "license": "MIT",
+  "require": {
+    "php": ">=8.0",
+    "posthog/posthog-php": "^4.0"
+  },
+  "scripts": {
+    "start": "php todo.php"
+  }
+}