Both Pure Enums and Backed Enums implement an internal interface named
UnitEnum. UnitEnum includes a static method
cases(). cases() returns a packed array of
all defined Cases in the order of declaration.
<?phpSuit::cases();// Produces: [Suit::Hearts, Suit::Diamonds, Suit::Clubs, Suit::Spades]?>Manually defining a cases() method on an Enum will result in a fatal error.