> ## Documentation Index
> Fetch the complete documentation index at: https://docs.growthbook.io/llms.txt
> Use this file to discover all available pages before exploring further.

# PHP SDK

> Install the GrowthBook PHP SDK to evaluate feature flags and run A/B tests in PHP applications, including targeting attributes and tracking callbacks.

The GrowthBook PHP SDK requires PHP version 8.0 or greater.

php

PHP SDK Resources

Get help on Slack

## Installation

GrowthBook is available on Composer:

```bash theme={null}
composer require growthbook/growthbook
```

## Quick Usage

```php theme={null}
// Create a GrowthBook instance
$growthbook = Growthbook\Growthbook::create()
  ->withAttributes([
    // Targeting attributes
    'id' => $userId,
    'someCustomAttribute' => true
  ]);

// Load feature flags from the GrowthBook API
// Make sure to use caching in production! (see 'Loading Features' below)
// Note: Prior to version 1.7.0, this method was called `loadFeatures` instead of `initialize`
$growthbook->initialize("sdk-abc123", "https://cdn.growthbook.io");

// Feature gating
if ($growthbook->isOn("my-feature")) {
  echo "It's on!";
} else {
  echo "It's off :(";
}

// Remote configuration with fallback
$color = $growthbook->getValue("button-color", "blue");
echo "<button style='color:${color}'>Click Me!</button>";
```

Some of the feature flags you evaluate might be running an A/B test behind the scenes which you'll want to track in your analytics system.

At the end of the request, you can loop through all experiments and track them however you want to:

```php theme={null}
$impressions = $growthbook->getViewedExperiments();
foreach($impressions as $impression) {
  // Whatever you use for event tracking
  Segment::track([
    "userId" => $userId,
    "event" => "Experiment Viewed",
    "properties" => [
      "experimentId" => $impression->experiment->key,
      "variationId" => $impression->result->key
    ]
  ]);
}
```

### Loading Features

There are 2 ways to load features into the SDK. You can use `initialize` with a Client Key and API Host. Or, you can manually fetch and cache feature flags and pass them in with the `withFeatures` method.

#### initialize method

The `initialize` method can fetch features from the GrowthBook API for you.

By default, there is no caching enabled. You can enable it by passing any PSR16-compatible instance into the `withCache` method.

**Caching is required for production usage**

```php theme={null}
// Any psr-16 library will work
use Cache\Adapter\Apcu\ApcuCachePool;

$cache = new ApcuCachePool();

$growthbook = Growthbook\Growthbook::create()
  ->withCache($cache);

// You can optionally pass in a TTL (default 60s)
$growthbook = Growthbook\Growthbook::create()
  ->withCache($cache, 120); // Cache for 120s instead
```

To load features, we require a PSR-17 (HttpClient) and PSR-18 (RequestFactoryInterface) compatible library like Guzzle to be installed.

We will auto-discover most HTTP libraries without any configuration required, but if you prefer to specify it explicitly, you can use the `withHttpClient` method. Note - you'll need to specify both an `HttpClient` and a `RequestFactoryInterface` implementation.

The `initialize` method takes 3 arguments:

* `$clientKey` (required) - Get this from your SDK Connection in GrowthBook.
* `$apiHost` (optional) - Defaults to `https://cdn.growthbook.io`. If self-hosting GrowthBook, set this to your API host.
* `$decryptionKey` (optional) - Only required if you've enabled encryption for your SDK Connection.

#### withFeatures method

If you prefer to have full control over the fetching/caching behavior, you can use the `withFeatures` method instead to pass an associative array of features into the SDK.

#### withSavedGroups method

If you're using saved groups and not using the `initialize` method, you'll need to call `withSavedGroups` to provide the saved groups data to the SDK.

```php theme={null}
// From the GrowthBook API, a custom cache layer, or somewhere else
$featuresJSON = '{"my-feature":{"defaultValue":true}}';

// Decode into an associative array
$features = json_decode($featuresJSON, true);

// Pass into the Growthbook instance
$growthbook = Growthbook\Growthbook::create()
  ->withFeatures($features);

// Optionally, if using saved groups
$savedGroupsJSON = '{"myGroup": [1, 2, 3]}';
$savedGroups = json_decode($savedGroupsJSON, true);
$growthbook = $growthbook->withSavedGroups($savedGroups);
```

## The Growthbook Class

The `Growthbook` class has a number of properties. These can be set using a Fluent interface or can be passed into a constructor using an associative array. Every property also has a getter method if needed. Here's an example:

```php theme={null}
// Using the fluent interface
$growthbook = Growthbook\Growthbook::create()
  ->withFeatures($features)
  ->withAttributes($attributes);

// Using the constructor
$growthbook = new Growthbook\Growthbook([
  'features' => $features,
  'attributes' => $attributes
]);

// Getter methods
print_r($growthbook->getFeatures());
print_r($growthbook->getAttributes());
```

Note: you can also use the fluent methods (e.g. `withFeatures`) at any point to update properties.

### Attributes

You can specify attributes about the current user and request. These are used for two things:

1. Feature targeting (e.g. paid users get one value, free users get another)
2. Assigning persistent variations in A/B tests (e.g. user id "123" always gets variation B)

Attributes can be any JSON data type - boolean, integer, float, string, or array.

```php theme={null}
$attributes = [
  'id' => "123",
  'loggedIn' => true,
  'deviceId' => "abc123def456",
  'age' => 21,
  'tags' => ["tag1", "tag2"],
  'account' => [
    'age' => 90
  ]
];
```

If you want to update attributes later, please note that the `withAttributes` method completely overwrites the attributes object. You can use `array_merge` if you only want to update a subset of fields:

```php theme={null}
// Only update the url attribute
$growthbook->withAttributes(array_merge(
  $growthbook->getAttributes(),
  [
    'url' => '/checkout'
  ]
));
```

### Tracking Experiments

Any time an experiment is run to determine the value of a feature, you want to track that event in your analytics system.

You can either do this via a callback function:

```php theme={null}
$trackingCallback = function (
  Growthbook\InlineExperiment $experiment,
  Growthbook\ExperimentResult $result
) {
  // Segment.io example
  Segment::track([
    "userId" => $userId,
    "event" => "Experiment Viewed",
    "properties" => [
      "experimentId" => $experiment->key,
      "variationId" => $result->key
    ]
  ]);
};

// Fluent interface
$growthbook = Growthbook\Growthbook::create()
  ->withTrackingCallback($callback);

// Using the constructor
$growthbook = new Growthbook([
  'trackingCallback' => $trackingCallback
]);

// Getter method
$trackingCallback = $growthbook->getTrackingCallback();
```

Or track all events at the end of the request by looping through an array:

```php theme={null}
$impressions = $growthbook->getViewedExperiments();
foreach($impressions as $impression) {
  // Segment.io example
  Segment::track([
    "userId" => $userId,
    "event" => "Experiment Viewed",
    "properties" => [
      "experimentId" => $impression->experiment->key,
      "variationId" => $impression->result->key
    ]
  ]);
}
```

Or, you can pass the impressions onto your front-end and fire analytics events from there. To do this, simply add a block to your template (shown here in plain PHP, but similar idea for Twig, Blade, etc.).

```php theme={null}
<script>
<?php foreach($growthbook->getViewedExperiments() as $impression): ?>
  // tracking code goes here
<?php endforeach; ?>
</script>
```

Below are examples for a few popular front-end tracking libraries:

#### Google Analytics

```php theme={null}
ga('send', 'event', 'experiment',
  "<?= $impression->experiment->key ?>",
  "<?= $impression->result->variationId ?>",
  {
    // Custom dimension for easier analysis
    'dimension1': "<?=
      $impression->experiment->key.':'.$impression->result->key
    ?>"
  }
);
```

#### Segment

```php theme={null}
analytics.track("Experiment Viewed", <?=json_encode([
  "experimentId" => $impression->experiment->key,
  "variationId" => $impression->result->key
])?>);
```

#### Mixpanel

```php theme={null}
mixpanel.track("Experiment Viewed", <?=json_encode([
  'Experiment name' => $impression->experiment->key,
  'Variant name' => $impression->result->key
])?>);
```

### GrowthBook Event Tracking

Sends experiment view and feature usage events to GrowthBook's [Managed Warehouse](https://docs.growthbook.io/app/managed-warehouse.md) or [Event Forwarder](https://docs.growthbook.io/app/event-forwarder.md).

Requires `growthbook/growthbook` v2.4.0 or later.

```php theme={null}
use Growthbook\Growthbook;
use Growthbook\GrowthBookTrackingPlugin;
use Growthbook\GrowthBookTrackingPluginConfig;

$growthbook = Growthbook::create()
  ->withAttributes(['id' => $userId])
  ->addPlugin(new GrowthBookTrackingPlugin(
    new GrowthBookTrackingPluginConfig(
      ingestorHost: "https://us-east-1.gb-ingest.com",
    )
  ));

$growthbook->initialize("YOUR_CLIENT_KEY");
```

Call `addPlugin()` after any `with*()` methods. Those return a copy of the instance, and a discarded copy closes the plugin. The plugin gets its client key from `initialize()`, and pending events are sent when the request ends.

Custom events aren't supported yet. Send them with the [Ingestion API](https://docs.growthbook.io/app/managed-warehouse.md#ingestion-api).

| Option | Description |
| - | - |
| `ingestorHost` | Ingestor for your Data Region. |
| `batchSize` | Events to queue before sending mid-request. Default `100`. |

### Logging

GrowthBook can output log messages to help you debug your feature flags and experiments.

We support any PSR-3 compatible logger. We implement a fluent interface (`withLogger`) as well as the standard LoggerAware interface (`setLogger`).

```php theme={null}
// Fluent interface
$growthbook
  ->withLogger($logger)
  ->with...;

// Setter
$growthbook->setLogger($logger);
```

## Using Features

There are 3 main methods for interacting with features.

* `$growthbook->isOn("feature-key")` returns true if the feature is on
* `$growthbook->isOff("feature-key")` returns false if the feature is on
* `$growthbook->getValue("feature-key", "default")` returns the value of the feature with a fallback

In addition, you can use `$growthbook->getFeature("feature-key")` to get back a `FeatureResult` object with the following properties:

* **value** - The JSON-decoded value of the feature (or `null` if not defined)
* **on** and **off** - The JSON-decoded value cast to booleans
* **source** - Why the value was assigned to the user. One of `unknownFeature`, `defaultValue`, `force`, or `experiment`
* **experiment** - Information about the experiment (if any) which was used to assign the value to the user
* **experimentResult** - The result of the experiment (if any) which was used to assign the value to the user

## Sticky Bucketing

By default GrowthBook does not persist assigned experiment variations for a user. We rely on deterministic hashing to ensure that the same user attributes always map to the same experiment variation. However, there are cases where this isn't good enough. For example, if you change targeting conditions in the middle of an experiment, users may stop being shown a variation even if they were previously bucketed into it.

Sticky Bucketing is a solution to these issues. You can provide a Sticky Bucket Service to the GrowthBook instance to persist previously seen variations and ensure that the user experience remains consistent for your users.

A sample `InMemoryStickyBucketService` implementation is provided for reference, but in production you will definitely want to implement your own version using a database, cookies, or similar for persistence.

Sticky Bucket documents contain three fields

* `attributeName` - The name of the attribute used to identify the user (e.g. `id`, `cookie_id`, etc.)
* `attributeValue` - The value of the attribute (e.g. `123`)
* `assignments` - A dictionary of persisted experiment assignments. For example: `{"exp1__0":"control"}`

The attributeName/attributeValue combo is the primary key.

Here's an example implementation using a theoretical `db` object:

```php theme={null}
class InMemoryStickyBucketService extends StickyBucketService
{
    /** @var array<string, StickyAssignmentDocument>  */
    public array $docs = [];

    /**
     * @param string $attributeName
     * @param mixed $attributeValue
     * @return StickyAssignmentDocument|null
     */
    public function getAssignments(string $attributeName, $attributeValue): ?StickyAssignmentDocument
    {
        return $this->docs[$this->getKey($attributeName, $attributeValue)] ?? null;
    }

    /**
     * @param StickyAssignmentDocument $doc
     * @return void
     */
    public function saveAssignments(StickyAssignmentDocument $doc): void
    {
        $this->docs[$this->getKey($doc->getAttributeName(), $doc->getAttributeValue())] = $doc;
    }

    /**
     * @return void
     */
    public function destroy(): void
    {
        $this->docs = [];
    }
}

// Fluent interface
$growthbook = Growthbook\Growthbook::create()
  ->withStickyBucketing(new InMemoryStickyBucketService());

// Using the constructor
$growthbook = new Growthbook([
  'stickyBucketService' => new InMemoryStickyBucketService()
]);
```

## Inline Experiments

Instead of declaring all features up-front and referencing them by ids in your code, you can also just run an experiment directly. This is done with the `$growthbook->runInlineExperiment` method:

```php theme={null}
$exp = Growthbook\InlineExperiment::create(
  "my-experiment",
  ["red", "blue", "green"]
);

// Either "red", "blue", or "green"
echo $growthbook->runInlineExperiment($exp)->value;
```

As you can see, there are 2 required parameters for experiments, a string key, and an array of variations. Variations can be any data type, not just strings.

There are a number of additional settings to control the experiment behavior. The methods are all chainable. Here's an example that shows all of the possible settings:

```php theme={null}
$exp = Growthbook\InlineExperiment::create("my-experiment", ["red","blue"])
  // Run a 40/60 experiment instead of the default even split (50/50)
  ->withWeights([0.4, 0.6])
  // Only include 20% of users in the experiment
  ->withCoverage(0.2)
  // Targeting conditions using a MongoDB-like syntax
  ->withCondition([
    'country' => 'US',
    'browser' => [
      '$in' => ['chrome', 'firefox']
    ]
  ])
  // Use an alternate attribute for assigning variations (default is 'id')
  ->withHashAttribute("sessionId")
  // Namespaces are used to run mutually exclusive experiments
  // Another experiment in the "pricing" namespace with a non-overlapping range
  //   will be mutually exclusive (e.g. [0.5, 1])
  ->withNamespace("pricing", 0, 0.5);
```

### Inline Experiment Return Value

A call to `runInlineExperiment` returns an `ExperimentResult` object with a few useful properties:

```php theme={null}
$result = $growthbook->runInlineExperiment($exp);

// If user is part of the experiment
echo($result->inExperiment); // true or false

// The index of the assigned variation
echo($result->variationId); // e.g. 0 or 1

// The key used to identify this variation when tracking the event
echo($result->key); // e.g. "control"

// The value of the assigned variation
echo($result->value); // e.g. "A" or "B"

// If the variations was randomly assigned based on a hash
echo($result->hashUsed); // true or false

// The user attribute that was hashed
echo($result->hashAttribute); // "id"

// The value of that attribute
echo($result->hashValue); // e.g. "123"
```

The `inExperiment` flag will be false if the user was excluded from being part of the experiment for any reason (e.g. failed targeting conditions).

The `hashUsed` flag will only be true if the user was randomly assigned a variation. If the user was forced into a specific variation instead, this flag will be false.

## Supported Features