laravel:constants-and-configuration

Constants and Configuration Values

Avoid hardcoded values throughout your codebase. Use constants, configuration files, and enums to make your application more maintainable, refactorable, and debuggable.

The Problem with Hardcoded Values

// BAD: Magic numbers and strings scattered everywhere
if ($user->role === 'admin') { // What other roles exist?
    $cacheTime = 3600; // What does 3600 mean?
}

if ($order->status === 1) { // What does 1 represent?
    $discount = 0.15; // Why 15%?
}

Cache::remember('users_list', 600, fn() => ...); // 600 what?

Solution 1: PHP Constants and Enums

Class Constants

// app/Constants/UserRole.php
class UserRole
{
    public const ADMIN = 'admin';
    public const EDITOR = 'editor';
    public const VIEWER = 'viewer';
    public const GUEST = 'guest';

    public const ALL = [
        self::ADMIN,
        self::EDITOR,
        self::VIEWER,
        self::GUEST,
    ];

    public static function hasPermission(string $role, string $action): bool
    {
        return match($role) {
            self::ADMIN => true,
            self::EDITOR => in_array($action, ['read', 'write', 'edit']),
            self::VIEWER => $action === 'read',
            self::GUEST => false,
            default => false,
        };
    }
}

// Usage
if ($user->role === UserRole::ADMIN) {
    // Clear intent
}

PHP 8.1+ Enums

// app/Enums/OrderStatus.php
enum OrderStatus: string
{
    case PENDING = 'pending';
    case PROCESSING = 'processing';
    case SHIPPED = 'shipped';
    case DELIVERED = 'delivered';
    case CANCELLED = 'cancelled';
    case REFUNDED = 'refunded';

    public function label(): string
    {
        return match($this) {
            self::PENDING => 'Pending Payment',
            self::PROCESSING => 'Processing',
            self::SHIPPED => 'Shipped',
            self::DELIVERED => 'Delivered',
            self::CANCELLED => 'Cancelled',
            self::REFUNDED => 'Refunded',
        };
    }

    public function color(): string
    {
        return match($this) {
            self::PENDING => 'yellow',
            self::PROCESSING => 'blue',
            self::SHIPPED => 'indigo',
            self::DELIVERED => 'green',
            self::CANCELLED => 'red',
            self::REFUNDED => 'gray',
        };
    }

    public function canTransitionTo(self $newStatus): bool
    {
        return match($this) {
            self::PENDING => in_array($newStatus, [
                self::PROCESSING,
                self::CANCELLED,
            ]),
            self::PROCESSING => in_array($newStatus, [
                self::SHIPPED,
                self::CANCELLED,
            ]),
            self::SHIPPED => $newStatus === self::DELIVERED,
            self::DELIVERED => $newStatus === self::REFUNDED,
            default => false,
        };
    }
}

// Model with enum casting
class Order extends Model
{
    protected $casts = [
        'status' => OrderStatus::class,
    ];

    public function transitionTo(OrderStatus $newStatus): void
    {
        if (!$this->status->canTransitionTo($newStatus)) {
            throw new InvalidStateTransition(
                "Cannot transition from {$this->status->value} to {$newStatus->value}"
            );
        }

        $this->update(['status' => $newStatus]);
    }
}

// Usage
$order->transitionTo(OrderStatus::PROCESSING);