LaunchDarkly Developer Documentation

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PHP SDK Reference

This reference guide documents all of the methods available in our PHP SDK, and explains in detail how these methods work. If you want to dig even deeper, our SDKs are open source-- head to our PHP SDK repository on GitHub.

Getting started

Requirements

PHP 5.5 or higher.

If you haven't taken a look at our Quickstart guide yet, we recommend starting there to see how install our SDK into your PHP application.

Once the SDK is installed, you'll want to create a single, shared instance of LDClient:

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

Fetching Flags

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

We strongly suggest using the ld-relay. Per-flag caching mode (Guzzle) is only intended for low-throughput environments.

Using Guzzle

Require Guzzle as a dependency:

php composer.phar require "guzzlehttp/guzzle:6.2.1"
php composer.phar require "kevinrob/guzzle-cache-middleware:1.4.1"

It will then be used as the default way of fetching flags.

With Guzzle, you could persist your cache somewhere other than the default in-memory store, like Memcached or Redis.

You could then specify your cache when initializing the client with the cache option.

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

Using LD-Relay

Setup ld-relay in daemon-mode with Redis

Require Predis as a dependency:

php composer.phar require "predis/predis:1.0.*"

Create the LDClient with the Redis feature requester as an option:

$client = new LaunchDarkly\LDClient("your_sdk_key", ['feature_requester_class' => 'LaunchDarkly\LDDFeatureRequester', 'redis_host' => 'your.redis.host', 'redis_port' => 6379]);

Caching and PHP

PHP's shared-nothing architecture means that the out-of-the-box in-memory HTTP cache used by our SDK won't cache feature flags across requests.

In production, we strongly recommend the ld-relay for PHP.

Customizing your client

In an earlier example, we passed a cache option as an array to the client constructor. There are a few additional options you can set in this array. Here's an example:

$client = new LaunchDarkly\LDClient("YOUR_SDK_KEY", array("cache" => $cacheStorage, "connect_timeout" => 3));

We've set the client connect timeout to 3 seconds in addition to providing a custom cache storage provider. The complete list of customizable parameters is as follows:

  • connect_timeout: Must be a number, in seconds, and controls the connection timeout to LaunchDarkly
  • timeout: Must be a number, in seconds, and controls the end-to-end request timeout to LaunchDarkly
  • capacity: Must be a number, and controls the maximum size of the event buffer. LaunchDarkly sends events asynchronously, and buffers them for efficiency.

Sending events in PHP

The LaunchDarkly SDK sends data back to our server to record events from Track and Variation calls. On our other platforms, this data is sent asynchronously, so that it adds no latency to serving web pages.

Once again, PHP's shared-nothing architecture makes this a bit difficult. By default, LaunchDarkly forks an external process that executes curl to send this data. In practice we've found that this is the most reliable way to send data without introducing latency to page load times.

If your server does not have curl installed, or has other restrictions that make it impossible to invoke curl as an external process, you may need to implement a custom EventProcessor to send events to LaunchDarkly.

Users

Feature flag targeting and rollouts are all determined by the user you pass to your Variation calls. In our PHP SDK, we use a builder pattern to make it easy to construct users. Here's an example:

$user = (new LDUserBuilder("aa0ceb"))->firstName("Ernestina")->lastName("Evans")->email("ernestina@example.com")->custom(["groups" => array("Google","Microsoft")])->build();

Let's walk through this snippet. The first argument to the builder is the user's key-- in this case we've used the hash "aa0ceb". The user key is the only mandatory user attribute. The key should also uniquely identify each user. You can use a primary key, an e-mail address, or a hash, as long as the same user always has the same key. We recommend using a hash if possible.

All of the other attributes (like firstName, email, and the custom attributes) are optional. The attributes you specify will automatically appear on our dashboard, meaning that you can start segmenting and targeting users with these attributes.

Besides the key, LaunchDarkly supports the following attributes at the "top level". Remember, all of these are optional:

  • ip: Must be an IP address. If you provide an IP, LaunchDarkly will use a geolocation service to automatically infer a country for the user (unless you've already specified one).
  • firstName: Must be a string. If you provide a first name, you can search for users on the Users page by name.
  • lastName: Must be a string. If you provide a last name, you can search for users on the Users page by name.
  • country: Must be a string representing the country associated with the user.
  • email: Must be a string representing the user's e-mail address. If an avatar URL is not provided, we'll use Gravatar to try to display an avatar for the user on the Users page.
  • avatar: Must be an absolute URL to an avatar image for the user.
  • name: Must be a string. You can search for users on the User page by name
  • anonymous: Must be a boolean. See the section below on anonymous users for more details.

In addition to these, you can pass us any of your own user data by passing custom attributes, like the groups attribute in the example above.

A note on types

Most of our built-in attributes (like names and e-mail addresses) expect string values. Custom attributes values can be strings, booleans (like true or false), numbers, or lists of strings, booleans or numbers.

If you enter a custom value on our dashboard that looks like a number or a boolean, it'll be interpreted that way. The PHP SDK is strongly typed, so be aware of this distinction.

Custom attributes are one of the most powerful features of LaunchDarkly. They let you target users according to any data that you want to send to us-- organizations, groups, account plans-- anything you pass to us becomes available instantly on our dashboard.

Anonymous users

You can also distinguish logged-in users from anonymous users in the SDK, as follows:

$user = (new LDUserBuilder("aa0ceb"))->anonymous(true)->build();

You will still need to generate a unique key for anonymous users-- session IDs or UUIDs work best for this.

Anonymous users work just like regular users, except that they won't appear on your Users page in LaunchDarkly. You also can't search for anonymous users on your Features page, and you can't search or autocomplete by anonymous user keys. This is actually a good thing-- it keeps anonymous users from polluting your Users page!

Variation

The variation method determines which variation of a feature flag a user receives.

$client->variation($key, $user, false);

variation calls take the feature flag key, an LDUser, and a default value.

The default value will only be returned if an error is encountered-- for example, if the feature flag key doesn't exist or the user doesn't have a key specified.

The variation call will automatically create a user in LaunchDarkly if a user with that user key doesn't exist already. There's no need to create users ahead of time (but if you do need to, take a look at Identify).

Track

The track method allows you to record actions your users take on your site. This lets you record events that take place on your server. In LaunchDarkly, you can tie these events to goals in A/B tests. Here's a simple example:

$client->track("Signed up", user);

You can also attach custom data (anything that can be marshaled to JSON) to your event by passing an extra parameter to track:

$client->track("Completed purchase", user, ["price" => 320]);

Identify

The identify creates or updates users on LaunchDarkly, making them available for targeting and autocomplete on the dashboard. In most cases, you won't need to call identify-- the variation call will automatically create users on the dashboard for you. identify can be useful if you want to pre-populate your dashboard before launching any features.

$client->identify(user);

All flags

Creating users

Note that unlike variation and identify calls, allFlags does not send events to LaunchDarkly. Thus, users are not created or updated in the LaunchDarkly dashboard.

The allFlags method produces a dictionary of feature flag keys to their values for a specific user.

This method can be useful for passing feature flags to your front-end. In particular, it can be used to provide bootstrap flag settings for our JavaScript SDK.

$client->allFlags();

Secure mode hash

The secureModeHash method computes an HMAC signature of a user signed with the client's SDK key. If you're using our JavaScript SDK for client-side flags, this method generates the signature you need for secure mode.

$client->secureModeHash(user);

Offline mode

In some situations, you might want to stop making remote calls to LaunchDarkly and fall back to default values for your feature flags. For example, if your software is both cloud-hosted and distributed to customers to run on premise, it might make sense to fall back to defaults when running on premise. setOffline lets you do this easily.

$client = new LaunchDarkly\LDClient("YOUR_SDK_KEY", array("offline" => true));
$client->variation("any.feature.flag", user, false); // will always return the default value (false)

Logging

The PHP SDK uses Monolog. All loggers are namespaced under LaunchDarkly. A custom logger may be passed to the SDK via the configurable logger property:

$client = new LaunchDarkly\LDClient("YOUR_SDK_KEY", array("logger" => new Logger("LaunchDarkly", [new ErrorLogHandler(0, Logger::DEBUG)])));

Be aware of two considerations when enabling the DEBUG log level:

  1. Debug-level logs can be very verbose. It is not recommended that you turn on debug logging in high-volume environments.
  2. Potentially sensitive information is logged including LaunchDarkly users created by you in your usage of this SDK.

PHP SDK Reference