phputil/flags

🚩 A lightweight, customizable feature flags framework for PHP

You can customize:

• 🧠 How flags are evaluated, through Strategies.
• 💾 How flags are stored, through Storages.
• 📢 Who is notified about flag changes or removal, through Listeners.

Installation

PHP 7.4 or later. No external dependencies.

composer require phputil/flags

👉 You may also like to install some of the official extensions.

Extensions

Official extensions:

• phputil/flags-pdo - a PDO-based storage.
• ⏳ SOON - phputil/flags-firebase - a Firebase-based storage.
• phputil/flags-webhooks a listener that works like a webhook, by notifying external APIs about flags' changes.

Third-party extensions:

• Create yours and open an Issue to be evaluated. It may appear here.

Usage

Basic flag checking:

require_once 'vendor/autoload.php';
use phputil\flags\FlagManager;

// By default, it uses a storage-based strategy with an in-memory storage
$flag = new FlagManager();

if ( $flag->isEnabled( 'my-cool-feature' ) ) {
    echo 'Cool feature available!', PHP_EOL;
} else {
    echo 'Not-so-cool feature here', PHP_EOL;
}

Customizing a certain verification:

// ...
use phputil\flags\FlagVerificationStrategy;

$flag = new FlagManager();

$myLuckBasedStrategy = new class implements FlagVerificationStrategy {
    function isEnabled( string $flag ): bool {
        return rand( 1, 100 ) >= 50; // 50% chance
    }
};

if ( $flag->isEnabled( 'my-cool-feature', [ $myLuckBasedStrategy ] ) ) {
    echo 'Cool feature available!', PHP_EOL;
} else {
    echo 'Not-so-cool feature here', PHP_EOL;
}

Customizing all the verifications:

$flag = new FlagManager( null, [ $myLuckBasedStrategy ] );

if ( $flag->isEnabled( 'my-cool-feature' ) ) {
    ...

Setting a flag:

$flag->enable( 'my-cool-feature' );
$flag->disable( 'my-cool-feature' );
$flag->setEnable( 'my-cool-feature', true /* or false */ );

Removing a flag:

$flag->remove( 'my-cool-feature' );

Retrieving flag data:

$flagData = $flag->getStorage()->get( 'my-cool-feature' ); // null if not found

Adding a listener:

// ...
use phputil\flags\FlagListener;
use phputil\flags\FlagData;

$myListener = new class implements FlagListener {
  public function notify( string $event, FlagData $flagData ): void {
    if ( $event === 'change' ) {
        echo 'Flag ', $flagData->key, ' is now ', $flagData->enabled ? 'enabled': 'disabled', PHP_EOL;
    } else if ( $event === 'removal' ) {
        echo 'Flag ', $flagData->key, ' was removed.', PHP_EOL;
    }
  }
};

$flag->addListener( $myListener ); // v0.5.0+
// or $flag->getListeners()->add( $myListener );

$flag->enable( 'my-cool-feature' ); // Notify the listener

Customization

Storages

Use a different flag storage by:

• Creating your own, extending FlagStorage; OR
• Using an external storage extension.

How to configure it:

$storage = /* Create your storage here, e.g. new InMemoryStorage() */;
$flag = new FlagManager( $storage );

Storages available in the framework:

• InMemoryStorage, that store flags in memory.

Strategies

Use a flag verification strategy by:

• Creating your own, extending FlagVerificationStrategy; OR
• Using an external strategy extension.

How to configure it globally:

$strategies = [ /* pass your strategies here   */ ];
$flag = new FlagManager( null, $strategies );

Strategies available in the framework:

• StorageBasedVerificationStrategy, that checks flags in a storage.
• EnvBasedVerificationStrategy, that checks flags based on environment variables.

👉 A flag is considered enabled when all the strategies considered it enabled.

Listeners

Define a listener by:

• Creating your own, extending FlagListener; OR
• Using an external listener extension.

How to configure it:

$flag->addListener( $myListener ); // v0.5.0+
// or $flag->getListeners()->add( $myListener );

Roadmap

• Extensible library
• Official extensions:
  • PDO-based storage
  • Firebase-based storage
  • Webhook-like listener
• REST API (external repository)
• Web-based control panel (external repository)

License

MIT © Thiago Delgado Pinto