Tommy Mühle | tommy-muehle.io Enums An introduction 1 

Tommy Mühle | tommy-muehle.io Tommy Mühle
 Software Engineer and Author 2 

Tommy Mühle | tommy-muehle.io What is an enum? 3 

Tommy Mühle | tommy-muehle.io Tommy Mühle | tommy-muehle.io … a data type consisting of a set of named values called elements … of the type. 
 The enumerator names are usually identifiers that behave as constants in the language. https:/ /en.wikipedia.org/wiki/Enumerated_type 

Tommy Mühle | tommy-muehle.io How they are implemented in PHP? 5 

Tommy Mühle | tommy-muehle.io There is no native implementation 6 

Tommy Mühle | tommy-muehle.io 7 https:/ /wiki.php.net/rfc/enum 

Tommy Mühle | tommy-muehle.io 8 https:/ /docs.hhvm.com/hack/enums/introduction 

Tommy Mühle | tommy-muehle.io Without enum classes 9 

Tommy Mühle | tommy-muehle.io 10 Avoid global constants // app.php const STATE_ACTIVE = 'active'; const STATE_COMPLETED = 'completed'; $app = new Application(); $app->setState(STATE_ACTIVE); // ... return $app->run(); 

Tommy Mühle | tommy-muehle.io 11 class StateHandler { const STATE_ACTIVE = 'active'; const STATE_CANCELED = 'canceled'; public function handle($state) { if ($state !== self::STATE_ACTIVE) { // ... } // ... } } Avoid class constants 

Tommy Mühle | tommy-muehle.io With enum classes 12 

Tommy Mühle | tommy-muehle.io 13 final class Color { const __DEFAULT = 'black'; const RED = 'red'; private $value; public function __construct(string $color = null) { $this->value = $color ?? self::__DEFAULT; } public function __toString() { return $this->value; } } 

Tommy Mühle | tommy-muehle.io Advantages 14 

Tommy Mühle | tommy-muehle.io You can get a list of all the values 15 

Tommy Mühle | tommy-muehle.io 16 final class Color { // ... public function __construct(string $color = null) { $value = $color ?? self::__DEFAULT; if (!in_array($value, $this->all(), true)) { // ... } $this->value = $value; } public function all() : array { return (new \ReflectionClass(static::class))
 ->getConstants(); } // ... } 

Tommy Mühle | tommy-muehle.io You can type-hint 17 

Tommy Mühle | tommy-muehle.io 18 class Article { private $color; public function colorize(Color $color) { // ... } } 

Tommy Mühle | tommy-muehle.io You can enrich your classes with methods. 19 

Tommy Mühle | tommy-muehle.io 20 final class Color { // ... protected $value; // ... public function value() { return $this->value; } public function equals(Color $color) { // or any other business condition return $this->value === $color->value(); } } 

Tommy Mühle | tommy-muehle.io 21 final class Color { // ... protected $value; // ... public static function fromHex(string $hex) { // do something with $hex and get $color return new self($color); } public function format() { return 'My special color format'; } } 

Tommy Mühle | tommy-muehle.io You can extend this classes 22 

Tommy Mühle | tommy-muehle.io 23 // if class Color are not final final class SpecialColor extends Color { // add further values, enrich methods, etc. } 

Tommy Mühle | tommy-muehle.io Before you start 24 

Tommy Mühle | tommy-muehle.io 25 https:/ /packagist.org/search/?q=enum 

Tommy Mühle | tommy-muehle.io Summary 26 

Questions? 

Thank you! Slides http:/ /bit.ly/2isVOvl Images https:/ /pixabay.com/ @tommy_muehle