PHP SDK reference

This topic documents how to get started with the server-side PHP SDK, and links to reference information on all of the supported features.

Overview

This topic documents how to get started with the PHP SDK, and links to reference information on all of the supported features.

LaunchDarkly’s SDKs are open source. In addition to this reference guide, we provide source, API reference documentation, and a sample application:

Resource	Location
SDK API documentation	SDK API docs
Supported SDK Versions	PHP SDK
GitHub repository	php-server-sdk
Sample application	PHP , OpenFeature PHP
Published module	Packagist

Get started

After you complete the Getting Started process, follow these instructions to start using the LaunchDarkly SDK in your PHP application.

Understand version compatibility

The LaunchDarkly PHP SDK, version 6.x and higher, is compatible with PHP 8.1 and higher. Starting with version 6.6, the LaunchDarkly PHP SDK also requires that the apcu extension is installed and enabled. The SDK uses the APCu cache to help improve performance.

If you are using older versions:

• The LaunchDarkly PHP SDK, version 5.x, is compatible with PHP 8.0 and higher.
• The LaunchDarkly PHP SDK, version 4.x, is compatible with PHP 7.3 and higher.
• If you need compatibility with older versions of PHP, use version 3.x of the LaunchDarkly PHP SDK.

Install the SDK

The first step is to install Composer and the LaunchDarkly SDK as a dependency in your application. Refer to the SDK releases page to identify the latest version if you want to depend on a specific version.

To install Composer:

Shell

    php composer.phar require launchdarkly/server-sdk

    # In earlier versions, this was "launchdarkly/launchdarkly-php"

Then require Composer’s autoloader:

PHP

    require 'vendor/autoload.php';

The PHP SDK uses an SDK key. Keys are specific to each project and environment. They are available from Project settings, on the Environments list. To learn more about key types, read Keys.

Initialize the client

After you install and import the SDK, create a single, shared instance of LDClient. Specify your SDK key here to authorize your application to connect to a particular environment within LaunchDarkly.

Only create one instance of client.

Here’s how:

PHP

    $client = new LaunchDarkly\LDClient("YOUR_SDK_KEY");

To learn more about the specific configuration options available in this SDK, read the SDK API documentation for the LDClient constructor.

Evaluate a context

You can use $client to check which variation a particular context will receive for a given feature flag.

Here’s how:

PHP

    $context = LDContext::builder("example-context-key")
      ->name("Sandy")
      ->build();

    if ($client->variation("your.flag.key", $context)) {
        // application code to show the feature
    } else {
        // the code to run if the feature is off
    }

In our Getting Started guide we recommend that users shut down the LaunchDarkly client on application termination. This step does not exist in PHP because the PHP SDK does not maintain long-lived network connections nor an event queue.

Fetch flags

There are two distinct methods of integrating LaunchDarkly in a PHP environment:

• The Relay Proxy retrieves and stores flags in Redis, DynamoDB, or Consul. This is the recommended method. If you use synced segments or larger list-based segments, you can only use Redis or DynamoDB as a persistent store.
• Guzzle Cache Middleware requests and caches HTTP responses in an in-memory array. This is the default method.

We strongly suggest using the Relay Proxy. Per-flag caching mode using Guzzle is only intended for low-throughput environments.

Using the Relay Proxy

PHP’s shared-nothing architecture prevents LaunchDarkly from reusing the streaming API connection across requests.

You can use PHP without the Relay Proxy, but we strongly recommend using the Relay Proxy in daemon mode if you are using PHP in a high-throughput setting. This makes the Relay Proxy receive feature flag updates.

To learn more, read Configuring SDKs to use different modes.

Using Guzzle

For the latest major version of the PHP SDK, use open-ended dependencies. For older versions, refer to your version’s composer.json file.

To require Guzzle as a dependency:

PHP

    php composer.phar require "guzzlehttp/guzzle:^6.3.0"
    php composer.phar require "kevinrob/guzzle-cache-middleware:^1.4.0"

Guzzle is then used to fetch flags. You can persist your cache somewhere other than the default in-memory store, like Memcached or Redis.

You can then specify your cache when initializing the client with the cache option:

PHP

    $client = new LaunchDarkly\LDClient("YOUR_SDK_KEY", ["cache" => $cacheStorage]);

Supported features

This SDK supports the following features:

• Anonymous contexts and users
• Big segments
• Configuration, including
  • Application metadata configuration
  • Migration configuration
  • Service endpoint configuration
• Context configuration
• Evaluating flags
• Flag evaluation reasons
• Flushing events
• Getting all flags
• Identifying and changing contexts
• Logging configuration
• Migrations
• Offline mode
• Private attributes
• Reading flags from a file
• Relay Proxy configuration
  • Using proxy mode
  • Using daemon mode
• Secure mode
• Sending custom events
• Storing data
• Test data sources