> ## Documentation Index
> Fetch the complete documentation index at: https://docs.lettr.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Getting Started
> Send transactional emails from any PHP app with the type-safe lettr/lettr-php SDK, featuring a fluent builder and typed error handling.
Send transactional emails from any PHP application using the official Lettr PHP SDK. The SDK provides a clean, type-safe interface for the Lettr API without requiring a specific framework.
The `lettr/lettr-php` package gives you a fluent interface for building and sending emails, managing templates, and tracking delivery — all with full IDE autocompletion and compile-time safety.
Using Cursor? [Jump straight in using this prompt](https://cursor.com/link/prompt?text=Help%20me%20add%20a%20Lettr%20sending%20example%20for%20PHP%20using%20lettr%2Flettr-php%2C%20or%20migrate%20my%20current%20PHP%20sending%20solution%20to%20Lettr%20using%20these%20docs%3A%20https%3A%2F%2Fdocs.lettr.com%2Fquickstart%2Fphp%2Fintroduction)
## Why Use the PHP SDK?
Rather than making raw HTTP requests, the SDK provides:
* **Type-safe API client** — Full IDE autocompletion and type hints for all methods
* **Fluent email builder** — Chainable methods for constructing complex emails
* **Template support** — Send Lettr-managed templates with merge tags and versioning
* **Error handling** — Typed exceptions for different API errors (validation, auth, not found)
* **Zero dependencies** — Only requires Guzzle HTTP client (which most PHP projects already use)
If you're using Laravel, consider using the framework-specific SDK instead for deeper integration: [Laravel SDK](/quickstart/laravel/introduction)
## Prerequisites
Before you begin, make sure you have:
Create an API key in the Lettr dashboard
Add and verify your sending domain
You'll also need:
* **PHP 8.4+** and **Composer** installed
* A verified sending domain in your [Lettr dashboard](https://app.lettr.com/domains)
## Quick Setup
The fastest way to get started is a three-step install, configure, and send process.
```bash theme={null}
composer require lettr/lettr-php
```
The package requires PHP 8.4+ and Guzzle 7.5+. Composer will install Guzzle automatically if it's not already in your project.
```php theme={null}
use Lettr\Lettr;
$lettr = Lettr::client('your-api-key');
```
Store your API key in environment variables or a config file, never hardcode it. API keys use the `lttr_` prefix followed by 64 hexadecimal characters.
```php theme={null}
$response = $lettr->emails()->send(
$lettr->emails()->create()
->from('sender@yourdomain.com', 'Your App')
->to(['recipient@example.com'])
->subject('Hello from Lettr')
->html('Hello!
This is a test email.
')
);
echo $response->requestId; // Request ID for tracking
echo $response->accepted; // Number of accepted recipients
```
The builder pattern lets you chain methods to construct your email. All emails require `from`, `to`, `subject`, and at least one content type (`html`, `text`, or a template).
The sender domain must be verified in your [Lettr dashboard](https://app.lettr.com/domains) before you can send emails. If you try to send from an unverified domain, the API returns a `422` validation error. See [Sending Domains](/learn/domains/sending-domains) for setup instructions.
## Verify Your API Key
Test that your API key is valid before sending emails:
```php theme={null}
$auth = $lettr->health()->authCheck();
echo $auth->teamId; // Your team ID
```
If no exception is thrown, you're authenticated and ready to send emails. This check verifies that your API key is correctly formatted, active, and has permission to access your team's resources.
During development, use the health check endpoint to catch configuration issues early. It's a quick way to verify your setup before attempting to send emails.
## Using a Framework?
If you're working within a specific PHP framework, these integrations provide deeper integration:
Mail facade integration, Mailables, and code generation
Use SMTP instead of the HTTP API
Send all WordPress emails through Lettr
## Section Overview
This quickstart is organized into focused pages:
| Page | What You'll Learn |
| ------------------------------------------------ | -------------------------------------------------------------------------------------- |
| [Installation](/quickstart/php/installation) | Package requirements, client setup, and verifying your installation |
| [Sending Emails](/quickstart/php/sending-emails) | All sending methods — HTML, text, templates, attachments, tracking, and error handling |
| [Templates](/quickstart/php/templates) | Managing Lettr templates, versioning, and retrieving merge tags |
| [Domains](/quickstart/php/domains) | Add, verify, and manage sending domains |
| [Webhooks](/quickstart/php/webhooks) | Create and manage webhook endpoints for delivery and engagement events |
| [Audience](/quickstart/php/audience) | Manage lists, contacts, topics, properties, and segments |
| [Campaigns](/quickstart/php/campaigns) | List, inspect, send, and schedule campaigns |
## What's Next
Detailed setup and client configuration
Learn all the ways to send emails
Work with Lettr-managed templates
Complete API documentation