PHP Enum

Built-in support for enums will be added in PHP 8.1.

Let’s imagine we have a car class Carand we would like to tell the exactly possible colors for it. How do you do it without enum ?

I think you use const as me. And than try to use this consts cases everywhere in the code.

class Color {
    public const RED   = "red";
    public const BLACK = "black";
    public const WHITE = "white";
}

And than in the code we use

(new Car())->setColor(Color::RED);

But the problem that if someone in the team does not know about this const Color and the project is large, there is a high probability he ll not use it.

Here php8.1 enum comes.

class Color {
    public const RED   = "red";
    public const BLACK = "black";
    public const WHITE = "white";
}

Now we can define class in this way

class Car {
    private Color $color;

    function setColor(Color $color): self {
        $this->color = $color;

        return $this;
    }
}

And we use

(new Car)->setColor(Color::RED);

Enum methods

Enums can define methods, just like classes. This is a very powerful feature, especially in combination with the match operator:

enum Color
{
    case RED;
    case BLACK;
    case WHITE;
    
    public function getColor(): string
    {
        return match($this) 
        {
            Color::RED => 'red',   
            Color::BLACK => 'black',   
            Color::WHITE => 'white',   
        };
    }
}

Methods can be used like so:

$color = Color::RED;
$color->color(); // 'red'

Enum interfaces

Enums can implement interfaces, just like normal classes:

interface HasColor
{
    public function getColor(): string;
}

enum Status implements HasColor
{
    case RED;
    case BLACK;
    case WHITE;
    
    public function getColor(): string { /* … */ }
}

Enum values type

We can tell the exactly expected types of values

Example with string

enum Color: string
{
    case RED = 'red';
    case BLACK = 'black';
    case WHITE = 'white';
}

Another example with int

enum PAYMENT: int
{
    case PENDING = 1;
    case CAPTURED = 2;
    case AUTHORISED = 3;
    case DONE = 4;
    case REFUNDED = 5;
}

Listing enum values

You can use the static Enum::cases() method to get a list of all available cases within an enum:

Color::cases();

and even more

foreach (Color::cases as $each) {
    // ...
}

Thank you for your attention.

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