FeatureFlags plugin for CakePHP

FeatureFlags is a CakePHP plugin that enables your to use feature flags in your application to enable functionality based on simple application config, or a more complex rule based system.

By using feature flags you can separate your code deployments from what features are enabled, or have different features enabled in different environments. For example, you could have features that are incomplete, enabled in staging environments but disabled in production.

Installation

You can install this plugin into your application using composer.

The recommended way to install composer packages is:

composer require markstory/cakephp-feature-flags

Next, load the plugin by running the following command:

bin/cake plugin load FeatureFlags

Usage

First you need to decide if you want simple boolean feature flags, or more complex rule based feature flags. For the examples below, we'll assume you have two features (calendar-v2, and checkout-v2) that you want to conditionally enable.

Simple Feature Flags

First create a configuration file config/features.php, with the following:

<?php
return [
    'Features' => [
        'calendar-v2' => true,
        'checkout-v2' => false,
    ],
];

In your Application::services() method add the following:

use FeatureFlags\FeatureManagerInterface;
use FeatureFlags\Simple\FeatureManager;

public function services(ContainerInterface $container): void
{
    $container->addShared(FeatureManagerInterface::class, function () {
        return new FeatureManager(Configure::read('Features'));
    });
}

With the DI container setup, you can have CakePHP inject the FeatureManager into your controllers, and commands as required.

public function view(FeatureManagerInterface $features, $id)
{
    if ($features->has('calendar-v2')) {
        // Logic for the new feature.
        return $this->render();
    }
    ...
}

Rule Based Feature Flags

First create a configuration file config/features.php, with the following:

<?php
return [
    'Features' => [
        // Each key is a feature name
        'calendar-v2' => [
            // Features are composed of many segments.
            // All conditions in a segment must match for a feature to be
            // granted
            'segments' => [
                // Segments can incrementally enable features
                'rollout' => 50,
                // Segments are composed of multiple conditions
                'conditions' => [
                    [
                        'property' => 'user_email',
                        'op' => 'equal',
                        'value' => 'winner@example.com',
                    ]
                ],
            ],
        ],
    ],
];

In your Application::services() method add the following:

use FeatureFlags\FeatureManagerInterface;
use FeatureFlags\RuleBased\FeatureManager;

public function services(ContainerInterface $container): void
{
    $container->addShared(FeatureManagerInterface::class, function () {
        return new FeatureManager(
            function (array $data) {
                $context = [];
                // Add properties to `$context` based on the data you use
                // to check features.
                return $context;
            }
            Configure::read('Features')
        );
    });
}

With the DI container setup, you can have CakePHP inject the FeatureManager into your controllers, and commands as required.

public function view(FeatureManagerInterface $features, $id)
{
    // Including application data in `features->has` calls allows
    // you to build custom feature logic that fits your application.
    $identity = $this->request->getAttribute('identity');
    if ($features->has('calendar-v2', ['user' => $identity])) {
        // Logic for the new feature.
        return $this->render();
    }
    ...
}

Writing conditions

Conditions will safely extract keys out of the context that your application prepares. Each condition compares a single attribute in your context to a known value.

[
    'property' => 'user_email',
    'op' => 'equal',
    'value' => 'winner@example.com',
]

The following op values are supported: