PHP - Enums

In PHP 8.1 and later, Enums (Enumerations) were introduced as a way to represent a set of named values, which is useful for defining constants that can only take one of a predefined list of values.

Basic Enum Example

php
<?php
    enum Status {
        case Active;
        case Inactive;
        case Pending;
    }
    
    // Usage
    $status = Status::Active;
    
    if ($status === Status::Active) {
        echo "The status is active.";
    }

In this example:

The enum Status defines three possible values (Active, Inactive, and Pending).
These values can be used as Status::Active, Status::Inactive, etc.

Backed Enums (Scalar Enums)

Enums can also have scalar values (int or string), known as backed enums. This allows enums to be mapped to a specific value.

Backed Enum Example (String)

php
<?php
    enum UserRole: string {
        case Admin = 'admin';
        case User = 'user';
        case Guest = 'guest';
    }
    
    // Usage
    $role = UserRole::Admin;
    echo $role->value;  // Outputs: admin

Backed Enum Example (Int)

php
<?php
    enum OrderStatus: int {
        case Pending = 0;
        case Shipped = 1;
        case Delivered = 2;
    }
    
    // Usage
    $status = OrderStatus::Shipped;
    echo $status->value;  // Outputs: 1

In these examples, enums are "backed" by specific scalar values (string or int), and the scalar value is accessible through the ->value property.

Methods in Enums

Enums can have methods, just like classes.

php
<?php
    enum PaymentStatus: string {
        case Pending = 'pending';
        case Completed = 'completed';
        case Failed = 'failed';
    
        // Method inside enum
        public function label(): string {
            return match($this) {
                self::Pending => 'Payment is pending',
                self::Completed => 'Payment completed successfully',
                self::Failed => 'Payment failed',
            };
        }
    }
    
    // Usage
    $status = PaymentStatus::Completed;
    echo $status->label();  // Outputs: Payment completed successfully

Static Methods in Enums

You can also define static methods to perform operations on enums.

php
<?php
    enum DaysOfWeek: string {
        case Monday = 'Mon';
        case Tuesday = 'Tue';
        case Wednesday = 'Wed';
    
        public static function fromString(string $day): ?self {
            return self::tryFrom($day) ?? null;
        }
    }
    
    // Usage
    $day = DaysOfWeek::fromString('Mon');
    echo $day->name;  // Outputs: Monday

Advantages of Using Enums

Type Safety: Enums restrict values to a specific set, reducing the chance of errors.
Improved Readability: Named constants are more descriptive than arbitrary integers or strings.
Code Organization: Enum members can have associated methods, providing a clean and structured way to encapsulate logic.

Enums are a powerful addition to PHP and are particularly useful in cases where you have a fixed set of related constants (e.g., status codes, days of the week, roles). Let me know if you'd like more specific examples!

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