README

Progressive is a feature flag library (also called toggle, switch, ...).
Thanks to Progressive, you can progressively, quickly and simply enable new features. (and just as quickly deactivate them in case of an emergency)

Installation

$ composer require antfroger/progressive

Usage

// From a file
$config = \Symfony\Component\Yaml\Yaml::parseFile('/your-own-config-file.yaml');
// Content of /your-own-config-file.yaml
// features:
//   dark-theme: true
//   call-center: false
//   homepage-v2:
//     enabled: true

// Or from a PHP array
$config = [
    'features' => [
        'dark-theme'  => true,
        'call-center' => false,
        'homepage-v2' => [
            'enabled' => true
        ],
    ]
];

$progressive = new Progressive($config);
$progressive->isEnabled('dark-theme');    // true
$progressive->isEnabled('call-center');   // false
$progressive->isEnabled('homepage-v2');   // true

Rules

Built-in

enabled: true|false

enabled enables (or disables) the feature for everyone, everywhere, all the time.
The value is meant to be a boolean, true|false.

// Short
$config = [
    'features' => [
        'dark-theme' => true
    ]
];

// Verbose
$config = [
    'features' => [
        'dark-theme'  => [
            'enabled' => true
        ]
    ]
];

Custom

You will probably need many more rules that will fit your needs and stack.

Let's say you want to redesign your homepage and progressively displaying it to test if everything goes right.
You start by enabling it in dev, then preprod, then prod but only for developers, then admins, then 1% of the users...
How would you be able to achieve that?

With custom rules!

$config = [
    'features' => [
        'homepage-v123'  => [
            'env' => ['DEV', 'PREPROD']
        ]
    ]
];
$progressive = new Progressive($config);

$progressive->addCustomRule('env', function (Context $context, array $envs) {
    return in_array(getenv('ENV'), $envs);
});

$progressive->isEnabled('homepage-v123'); // Returns true if ENV is DEV or PREPROD, otherwise returns false

(this lambda can be improved thanks to the Context object - more about it here)

Strategies

Rules are great but sometimes one rule is not enough to decide if a feature must be enabled.
You may want to enable a feature in PROD only for admins but to everyone in DEV, TEST and PREPROD.
Or you may want to enable a feature to the admins AND a given percentage of users.

That's where strategies come into play!

(Strategies are simply another name for nested rules.
And as for rules, you can create your own strategies!)

Progressive comes with two built-in strategies:

unanimous: []

unanimous enables the feature if all the conditions are met.
The value is meant to be an array of rules.

$config = [
    'features' => [
        'translate-interface'  => [
            'unanimous' => [
                'env'   => ['DEV', 'PREPROD'],
                'roles' => ['ROLE_ADMIN', 'ROLE_TRANSLATOR']
            ]
        ]
    ]
];

In this example, the interface to translate the app will only be displayed in DEV and PREPROD environments to users having ROLE_ADMIN or ROLE_TRANSLATOR as roles.
This strategy can be defined as an AND.

partial: []

partial enables the feature if only one of the conditions is met.
Rules are evaluated one by one. The feature is enabled as soon as one rule is true.
The value is meant to be an array of rules.

$config = [
    'features' => [
        'translate-interface'  => [
            'partial' => [
                'env'   => ['DEV', 'PREPROD'],
                'roles' => ['ROLE_ADMIN', 'ROLE_TRANSLATOR']
            ]
        ]
    ]
];

In this example, the interface to translate the app will be displayed:

• in DEV and PREPROD environments (for all users)
• for users having a role ROLE_ADMIN or ROLE_TRANSLATOR, regardless of the environment.

This strategy can be defined as an OR.

Context object

Progressive doesn't know anything of your application logic code (and doesn't want to know).
But you may want to use your logic inside custom rules.

In that case, the context object is your friend!
It's nothing more that an user-defined databag.

You can use it to improve our previous custom rule:

$context = new Context([
    'env' => getenv('ENV') ?: 'PROD'
]);

$config = [
    'features' => [
        'homepage-v123'  => [
            'env' => ['DEV', 'PREPROD']
        ]
    ]
];

$progressive = new Progressive($config, $context);
$progressive->addCustomRule('env', function (Context $context, array $envs) {
    return in_array($context->get('env'), $envs);
});

Another common example is to store the current user in the context:

$context = new Context(['user' => $user]);

$config = [
    'features' => [
        'homepage-v123'  => [
            'roles' => ['ROLE_ADMIN']
        ]
    ]
];

$progressive = new Progressive($config, $context);
$progressive->addCustomRule('roles', function (Context $context, array $roles) {
    $userRoles = $context->get('user')->getRoles();
    foreach ($roles as $role) {
        if (in_array($role, $userRoles) {
            return true;
        }
    }

    return false;
});

Requesting a non-existing flag

Whenever you request an non-existing flag, isEnabled will return false.
The flag is considered disabled.

$config = [
    'features' => []
];

$progressive = new Progressive($config);
$progressive->isEnabled('dark-theme'); // false

Separate feature releases from code deploy

As Progressive takes an array of config, it makes it possible to decorrelate the release calendar from the code deployment.
In this example, we use the Symfony Yaml component to read the config from a YAML file.

use Symfony\Component\Yaml\Yaml;

$config = Yaml::parseFile('/your-own-config-file.yaml');
// Content of /your-own-config-file.yaml
// features:
//   new-feature: false
$progressive = new Progressive($config);
$progressive->isEnabled('new-feature'); // false

Imagine that you are able to deploy the config files independently from your code base, you could release a new feature without having to deploy all your code base, by redeploying only /your-own-config-file.yaml.

// Content of /your-own-config-file.yaml
// features:
//   new-feature: true
$progressive->isEnabled('new-feature'); // true

You may also want to store the configuration in a database and pass it as an array to Progressive.

Progressive in your projects

• Progressive is also available as a Symfony bundle

Inspired by Laurent Callarec's javascript feature-flag library Banderole