PostHog Hello World Skill

PostHog Hello World

Overview

Minimal working examples demonstrating the three core PostHog operations: capturing events, identifying users, and evaluating feature flags. Covers both browser (posthog-js) and server (posthog-node) SDKs.

Prerequisites

Completed posthog-install-auth setup
Project API key (phc_...) configured
posthog-js and/or posthog-node installed

Instructions

Step 1: Capture Your First Event (Node.js)

// hello-posthog.ts
import { PostHog } from 'posthog-node';

const posthog = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, {
  host: 'https://us.i.posthog.com',
});

async function main() {
  // 1. Capture a custom event
  posthog.capture({
    distinctId: 'user-123',
    event: 'hello_posthog',
    properties: {
      greeting: 'Hello from posthog-node!',
      source: 'hello-world-skill',
      timestamp: new Date().toISOString(),
    },
  });
  console.log('Event captured: hello_posthog');

  // 2. Identify a user with properties
  posthog.identify({
    distinctId: 'user-123',
    properties: {
      email: 'dev@example.com',
      name: 'Dev User',
      plan: 'free',
    },
  });
  console.log('User identified: user-123');

  // 3. Check a feature flag
  const flagValue = await posthog.getFeatureFlag('my-feature-flag', 'user-123');
  console.log(`Feature flag "my-feature-flag": ${flagValue}`);

  // 4. Flush and shutdown (required in scripts/serverless)
  await posthog.shutdown();
  console.log('Done — check app.posthog.com Activity tab');
}

main().catch(console.error);

Step 2: Browser Hello World (posthog-js)

// In a React component or vanilla JS
import posthog from 'posthog-js';

// Initialize (call once at app startup)
posthog.init('phc_your_project_key', {
  api_host: 'https://us.i.posthog.com',
  loaded: () => console.log('PostHog loaded'),
});

// Capture a custom event
posthog.capture('button_clicked', {
  button_name: 'signup',
  page: window.location.pathname,
});

// Identify the user after login
posthog.identify('user-123', {
  email: 'user@example.com',
  plan: 'pro',
});

// Check a feature flag
if (posthog.isFeatureEnabled('new-checkout')) {
  console.log('New checkout flow is enabled');
}

// Associate user with a company (group analytics)
posthog.group('company', 'company-456', {
  name: 'Acme Corp',
  plan: 'enterprise',
});

Step 3: Python Hello World

import posthog

posthog.project_api_key = 'phc_your_project_key'
posthog.host = 'https://us.i.posthog.com'

# Capture event
posthog.capture('user-123', 'hello_posthog', {
    'greeting': 'Hello from Python!',
})

# Identify user
posthog.identify('user-123', {
    'email': 'dev@example.com',
    'plan': 'free',
})

# Feature flag
is_enabled = posthog.feature_enabled('my-flag', 'user-123')
print(f'Flag enabled: {is_enabled}')

Step 4: Raw HTTP API (No SDK)

set -euo pipefail
# Capture event via POST to /capture/
curl -X POST 'https://us.i.posthog.com/capture/' \
  -H 'Content-Type: application/json' \
  -d '{
    "api_key": "phc_your_project_key",
    "event": "hello_posthog",
    "distinct_id": "user-123",
    "properties": {
      "greeting": "Hello from curl!"
    }
  }'

# Batch capture multiple events
curl -X POST 'https://us.i.posthog.com/batch/' \
  -H 'Content-Type: application/json' \
  -d '{
    "api_key": "phc_your_project_key",
    "batch": [
      {"event": "page_viewed", "distinct_id": "user-123", "properties": {"page": "/home"}},
      {"event": "button_clicked", "distinct_id": "user-123", "properties": {"button": "cta"}}
    ]
  }'

Error Handling

| Error | Cause | Solution | |-------|-------|----------| | Events not in dashboard | Not flushed | Call await posthog.shutdown() or posthog.flush() | | posthog.init silently fails | Wrong API host | Use us.i.posthog.com (not app.posthog.com) | | Feature flag returns undefined | Flag not created yet | Create flag in PostHog dashboard first | | identify not linking | Different distinct_id | Frontend and backend must use the same distinct_id | | Python events missing | No flush before exit | posthog.shutdown() or posthog.flush() at end |

Output

Working event capture in PostHog Activity tab
User identified with properties in Persons view
Feature flag evaluation result logged
Console output confirming each operation

Resources

Next Steps

Proceed to posthog-local-dev-loop for development workflow setup.

Agent Skills: PostHog Hello World

Install this agent skill to your local

Skill Files