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laravel-constants-and-configuration

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Constants and Configuration Values

常量与配置值

Avoid hardcoded values throughout your codebase. Use constants, configuration files, and enums to make your application more maintainable, refactorable, and debuggable.
避免在代码库中使用硬编码值。使用常量、配置文件和枚举可以让你的应用程序更易于维护、重构和调试。

The Problem with Hardcoded Values

硬编码值的问题

php
// 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?
php
// 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

解决方案1：PHP常量与枚举

Class Constants

类常量

php
// 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
// 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

PHP 8.1+ 枚举

php
// 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);
php
// 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);

Solution 2: Configuration Files

解决方案2：配置文件

Application-Wide Settings

应用级全局设置

php
// config/app.php
return [
    'cache_ttl' => [
        'short' => 60,      // 1 minute
        'medium' => 300,    // 5 minutes
        'long' => 3600,     // 1 hour
        'day' => 86400,     // 24 hours
    ],

    'pagination' => [
        'default' => 20,
        'max' => 100,
        'options' => [10, 20, 50, 100],
    ],

    'upload' => [
        'max_file_size' => 10 * 1024 * 1024, // 10MB
        'allowed_extensions' => ['jpg', 'jpeg', 'png', 'pdf', 'doc', 'docx'],
        'storage_path' => 'uploads',
    ],

    'business' => [
        'tax_rate' => 0.08,
        'shipping_threshold' => 50.00,
        'discount_tiers' => [
            'bronze' => 0.05,
            'silver' => 0.10,
            'gold' => 0.15,
            'platinum' => 0.20,
        ],
    ],
];

// Usage
Cache::remember(
    'products',
    config('app.cache_ttl.long'),
    fn() => Product::all()
);

$maxSize = config('app.upload.max_file_size');
php
// config/app.php
return [
    'cache_ttl' => [
        'short' => 60,      // 1 minute
        'medium' => 300,    // 5 minutes
        'long' => 3600,     // 1 hour
        'day' => 86400,     // 24 hours
    ],

    'pagination' => [
        'default' => 20,
        'max' => 100,
        'options' => [10, 20, 50, 100],
    ],

    'upload' => [
        'max_file_size' => 10 * 1024 * 1024, // 10MB
        'allowed_extensions' => ['jpg', 'jpeg', 'png', 'pdf', 'doc', 'docx'],
        'storage_path' => 'uploads',
    ],

    'business' => [
        'tax_rate' => 0.08,
        'shipping_threshold' => 50.00,
        'discount_tiers' => [
            'bronze' => 0.05,
            'silver' => 0.10,
            'gold' => 0.15,
            'platinum' => 0.20,
        ],
    ],
];

// Usage
Cache::remember(
    'products',
    config('app.cache_ttl.long'),
    fn() => Product::all()
);

$maxSize = config('app.upload.max_file_size');

Feature-Specific Configuration

功能特定配置

php
// config/payment.php
return [
    'stripe' => [
        'key' => env('STRIPE_KEY'),
        'secret' => env('STRIPE_SECRET'),
        'webhook_secret' => env('STRIPE_WEBHOOK_SECRET'),
        'webhook_tolerance' => 300, // seconds
        'currency' => 'usd',
        'minimum_amount' => 50, // cents
    ],

    'retry' => [
        'max_attempts' => 3,
        'delay_seconds' => [5, 10, 30],
    ],

    'statuses' => [
        'pending' => 'pending',
        'processing' => 'processing',
        'succeeded' => 'succeeded',
        'failed' => 'failed',
    ],
];

// Usage in service
class PaymentService
{
    public function charge(int $amount): void
    {
        if ($amount < config('payment.stripe.minimum_amount')) {
            throw new InvalidAmountException('Amount below minimum');
        }

        // Process payment
    }
}
php
// config/payment.php
return [
    'stripe' => [
        'key' => env('STRIPE_KEY'),
        'secret' => env('STRIPE_SECRET'),
        'webhook_secret' => env('STRIPE_WEBHOOK_SECRET'),
        'webhook_tolerance' => 300, // seconds
        'currency' => 'usd',
        'minimum_amount' => 50, // cents
    ],

    'retry' => [
        'max_attempts' => 3,
        'delay_seconds' => [5, 10, 30],
    ],

    'statuses' => [
        'pending' => 'pending',
        'processing' => 'processing',
        'succeeded' => 'succeeded',
        'failed' => 'failed',
    ],
];

// Usage in service
class PaymentService
{
    public function charge(int $amount): void
    {
        if ($amount < config('payment.stripe.minimum_amount')) {
            throw new InvalidAmountException('Amount below minimum');
        }

        // Process payment
    }
}

Solution 3: Database-Driven Configuration

解决方案3：数据库驱动的配置

Settings Model

设置模型

php
// app/Models/Setting.php
class Setting extends Model
{
    protected $fillable = ['key', 'value', 'type'];

    protected $casts = [
        'value' => 'json',
    ];

    public static function get(string $key, mixed $default = null): mixed
    {
        return Cache::remember(
            "settings.{$key}",
            config('app.cache_ttl.long'),
            fn() => static::where('key', $key)->first()?->value ?? $default
        );
    }

    public static function set(string $key, mixed $value): void
    {
        static::updateOrCreate(
            ['key' => $key],
            ['value' => $value]
        );

        Cache::forget("settings.{$key}");
    }

    protected static function booted(): void
    {
        static::saved(function ($setting) {
            Cache::forget("settings.{$setting->key}");
        });
    }
}

// Usage
$maintenanceMode = Setting::get('maintenance_mode', false);
$maxLoginAttempts = Setting::get('max_login_attempts', 5);
php
// app/Models/Setting.php
class Setting extends Model
{
    protected $fillable = ['key', 'value', 'type'];

    protected $casts = [
        'value' => 'json',
    ];

    public static function get(string $key, mixed $default = null): mixed
    {
        return Cache::remember(
            "settings.{$key}",
            config('app.cache_ttl.long'),
            fn() => static::where('key', $key)->first()?->value ?? $default
        );
    }

    public static function set(string $key, mixed $value): void
    {
        static::updateOrCreate(
            ['key' => $key],
            ['value' => $value]
        );

        Cache::forget("settings.{$key}");
    }

    protected static function booted(): void
    {
        static::saved(function ($setting) {
            Cache::forget("settings.{$setting->key}");
        });
    }
}

// Usage
$maintenanceMode = Setting::get('maintenance_mode', false);
$maxLoginAttempts = Setting::get('max_login_attempts', 5);

Solution 4: Service Constants

解决方案4：服务常量

php
// app/Services/CacheService.php
class CacheService
{
    // Cache key patterns
    public const USER_KEY = 'user:%d';
    public const USER_POSTS_KEY = 'user:%d:posts';
    public const POST_KEY = 'post:%d';
    public const TRENDING_KEY = 'trending:%s:page:%d';

    // Cache tags
    public const TAG_USERS = 'users';
    public const TAG_POSTS = 'posts';
    public const TAG_COMMENTS = 'comments';

    public static function getUserKey(int $userId): string
    {
        return sprintf(self::USER_KEY, $userId);
    }

    public static function getUserPostsKey(int $userId): string
    {
        return sprintf(self::USER_POSTS_KEY, $userId);
    }

    public static function rememberUser(int $userId, Closure $callback)
    {
        return Cache::tags([self::TAG_USERS])->remember(
            self::getUserKey($userId),
            config('app.cache_ttl.medium'),
            $callback
        );
    }
}

// Usage
$user = CacheService::rememberUser($userId, fn() => User::find($userId));
php
// app/Services/CacheService.php
class CacheService
{
    // Cache key patterns
    public const USER_KEY = 'user:%d';
    public const USER_POSTS_KEY = 'user:%d:posts';
    public const POST_KEY = 'post:%d';
    public const TRENDING_KEY = 'trending:%s:page:%d';

    // Cache tags
    public const TAG_USERS = 'users';
    public const TAG_POSTS = 'posts';
    public const TAG_COMMENTS = 'comments';

    public static function getUserKey(int $userId): string
    {
        return sprintf(self::USER_KEY, $userId);
    }

    public static function getUserPostsKey(int $userId): string
    {
        return sprintf(self::USER_POSTS_KEY, $userId);
    }

    public static function rememberUser(int $userId, Closure $callback)
    {
        return Cache::tags([self::TAG_USERS])->remember(
            self::getUserKey($userId),
            config('app.cache_ttl.medium'),
            $callback
        );
    }
}

// Usage
$user = CacheService::rememberUser($userId, fn() => User::find($userId));

Solution 5: Validation Constants

解决方案5：验证常量

php
// app/Rules/ValidationRules.php
class ValidationRules
{
    public const NAME_REGEX = '/^[a-zA-Z\s\-\']+$/';
    public const PHONE_REGEX = '/^\+?[1-9]\d{1,14}$/';
    public const USERNAME_REGEX = '/^[a-zA-Z0-9_]{3,20}$/';
    public const SLUG_REGEX = '/^[a-z0-9\-]+$/';

    public const PASSWORD_MIN = 8;
    public const PASSWORD_MAX = 128;
    public const BIO_MAX = 500;
    public const COMMENT_MAX = 1000;

    public static function password(): array
    {
        return [
            'required',
            'string',
            'min:' . self::PASSWORD_MIN,
            'max:' . self::PASSWORD_MAX,
            Password::defaults(),
        ];
    }

    public static function username(): array
    {
        return [
            'required',
            'string',
            'regex:' . self::USERNAME_REGEX,
            'unique:users,username',
        ];
    }
}

// In FormRequest
public function rules(): array
{
    return [
        'username' => ValidationRules::username(),
        'password' => ValidationRules::password(),
        'bio' => ['nullable', 'string', 'max:' . ValidationRules::BIO_MAX],
    ];
}
php
// app/Rules/ValidationRules.php
class ValidationRules
{
    public const NAME_REGEX = '/^[a-zA-Z\s\-\']+$/';
    public const PHONE_REGEX = '/^\+?[1-9]\d{1,14}$/';
    public const USERNAME_REGEX = '/^[a-zA-Z0-9_]{3,20}$/';
    public const SLUG_REGEX = '/^[a-z0-9\-]+$/';

    public const PASSWORD_MIN = 8;
    public const PASSWORD_MAX = 128;
    public const BIO_MAX = 500;
    public const COMMENT_MAX = 1000;

    public static function password(): array
    {
        return [
            'required',
            'string',
            'min:' . self::PASSWORD_MIN,
            'max:' . self::PASSWORD_MAX,
            Password::defaults(),
        ];
    }

    public static function username(): array
    {
        return [
            'required',
            'string',
            'regex:' . self::USERNAME_REGEX,
            'unique:users,username',
        ];
    }
}

// In FormRequest
public function rules(): array
{
    return [
        'username' => ValidationRules::username(),
        'password' => ValidationRules::password(),
        'bio' => ['nullable', 'string', 'max:' . ValidationRules::BIO_MAX],
    ];
}

Solution 6: HTTP Status Constants

解决方案6：HTTP状态常量

php
// app/Http/Responses/ApiResponse.php
class ApiResponse
{
    // Standard HTTP codes as constants for clarity
    public const OK = 200;
    public const CREATED = 201;
    public const ACCEPTED = 202;
    public const NO_CONTENT = 204;
    public const BAD_REQUEST = 400;
    public const UNAUTHORIZED = 401;
    public const FORBIDDEN = 403;
    public const NOT_FOUND = 404;
    public const VALIDATION_ERROR = 422;
    public const SERVER_ERROR = 500;

    // Custom application codes
    public const CODE_SUCCESS = 1000;
    public const CODE_VALIDATION_FAILED = 2001;
    public const CODE_RESOURCE_NOT_FOUND = 2002;
    public const CODE_UNAUTHORIZED_ACTION = 2003;
    public const CODE_RATE_LIMITED = 2004;

    public static function success($data = null, string $message = 'Success'): JsonResponse
    {
        return response()->json([
            'success' => true,
            'code' => self::CODE_SUCCESS,
            'message' => $message,
            'data' => $data,
        ], self::OK);
    }

    public static function error(string $message, int $httpCode = self::BAD_REQUEST, int $appCode = null): JsonResponse
    {
        return response()->json([
            'success' => false,
            'code' => $appCode ?? $httpCode,
            'message' => $message,
        ], $httpCode);
    }
}

// Usage
return ApiResponse::success($user, 'User created successfully');
return ApiResponse::error('Resource not found', ApiResponse::NOT_FOUND);
php
// app/Http/Responses/ApiResponse.php
class ApiResponse
{
    // Standard HTTP codes as constants for clarity
    public const OK = 200;
    public const CREATED = 201;
    public const ACCEPTED = 202;
    public const NO_CONTENT = 204;
    public const BAD_REQUEST = 400;
    public const UNAUTHORIZED = 401;
    public const FORBIDDEN = 403;
    public const NOT_FOUND = 404;
    public const VALIDATION_ERROR = 422;
    public const SERVER_ERROR = 500;

    // Custom application codes
    public const CODE_SUCCESS = 1000;
    public const CODE_VALIDATION_FAILED = 2001;
    public const CODE_RESOURCE_NOT_FOUND = 2002;
    public const CODE_UNAUTHORIZED_ACTION = 2003;
    public const CODE_RATE_LIMITED = 2004;

    public static function success($data = null, string $message = 'Success'): JsonResponse
    {
        return response()->json([
            'success' => true,
            'code' => self::CODE_SUCCESS,
            'message' => $message,
            'data' => $data,
        ], self::OK);
    }

    public static function error(string $message, int $httpCode = self::BAD_REQUEST, int $appCode = null): JsonResponse
    {
        return response()->json([
            'success' => false,
            'code' => $appCode ?? $httpCode,
            'message' => $message,
        ], $httpCode);
    }
}

// Usage
return ApiResponse::success($user, 'User created successfully');
return ApiResponse::error('Resource not found', ApiResponse::NOT_FOUND);

Solution 7: Queue Priorities and Job Constants

解决方案7：队列优先级与任务常量

php
// app/Jobs/JobPriority.php
class JobPriority
{
    public const CRITICAL = 'critical';
    public const HIGH = 'high';
    public const NORMAL = 'default';
    public const LOW = 'low';

    public const MAX_TRIES = [
        self::CRITICAL => 5,
        self::HIGH => 3,
        self::NORMAL => 3,
        self::LOW => 1,
    ];

    public const TIMEOUT = [
        self::CRITICAL => 300,  // 5 minutes
        self::HIGH => 180,      // 3 minutes
        self::NORMAL => 120,    // 2 minutes
        self::LOW => 60,        // 1 minute
    ];
}

// app/Jobs/ProcessPayment.php
class ProcessPayment implements ShouldQueue
{
    public $tries = JobPriority::MAX_TRIES[JobPriority::HIGH];
    public $timeout = JobPriority::TIMEOUT[JobPriority::HIGH];

    public function __construct(
        public Payment $payment
    ) {}

    public function handle(): void
    {
        // Process payment
    }

    public function queue(): string
    {
        return JobPriority::HIGH;
    }
}
php
// app/Jobs/JobPriority.php
class JobPriority
{
    public const CRITICAL = 'critical';
    public const HIGH = 'high';
    public const NORMAL = 'default';
    public const LOW = 'low';

    public const MAX_TRIES = [
        self::CRITICAL => 5,
        self::HIGH => 3,
        self::NORMAL => 3,
        self::LOW => 1,
    ];

    public const TIMEOUT = [
        self::CRITICAL => 300,  // 5 minutes
        self::HIGH => 180,      // 3 minutes
        self::NORMAL => 120,    // 2 minutes
        self::LOW => 60,        // 1 minute
    ];
}

// app/Jobs/ProcessPayment.php
class ProcessPayment implements ShouldQueue
{
    public $tries = JobPriority::MAX_TRIES[JobPriority::HIGH];
    public $timeout = JobPriority::TIMEOUT[JobPriority::HIGH];

    public function __construct(
        public Payment $payment
    ) {}

    public function handle(): void
    {
        // Process payment
    }

    public function queue(): string
    {
        return JobPriority::HIGH;
    }
}

Environment-Specific Constants

环境特定常量

php
// app/Providers/AppServiceProvider.php
class AppServiceProvider extends ServiceProvider
{
    public function boot(): void
    {
        // Define environment-specific constants
        if (app()->environment('local', 'testing')) {
            Config::set('app.debug_mode', true);
            Config::set('app.cache_ttl.short', 1); // Shorter cache in dev
        }

        if (app()->environment('production')) {
            Config::set('app.debug_mode', false);
            Config::set('app.rate_limit', 60); // Stricter in production
        }
    }
}
php
// app/Providers/AppServiceProvider.php
class AppServiceProvider extends ServiceProvider
{
    public function boot(): void
    {
        // Define environment-specific constants
        if (app()->environment('local', 'testing')) {
            Config::set('app.debug_mode', true);
            Config::set('app.cache_ttl.short', 1); // Shorter cache in dev
        }

        if (app()->environment('production')) {
            Config::set('app.debug_mode', false);
            Config::set('app.rate_limit', 60); // Stricter in production
        }
    }
}

Testing with Constants

使用常量进行测试

php
test('order status transitions work correctly', function () {
    $order = Order::factory()->create([
        'status' => OrderStatus::PENDING
    ]);

    // Valid transition
    $order->transitionTo(OrderStatus::PROCESSING);
    expect($order->status)->toBe(OrderStatus::PROCESSING);

    // Invalid transition
    expect(fn() => $order->transitionTo(OrderStatus::PENDING))
        ->toThrow(InvalidStateTransition::class);
});

test('cache keys are consistent', function () {
    $userId = 123;

    $key1 = CacheService::getUserKey($userId);
    $key2 = sprintf(CacheService::USER_KEY, $userId);

    expect($key1)->toBe($key2)
        ->and($key1)->toBe('user:123');
});

test('validation rules are applied correctly', function () {
    $data = ['username' => 'ab']; // Too short

    $validator = Validator::make($data, [
        'username' => ValidationRules::username()
    ]);

    expect($validator->fails())->toBeTrue();
});
php
test('order status transitions work correctly', function () {
    $order = Order::factory()->create([
        'status' => OrderStatus::PENDING
    ]);

    // Valid transition
    $order->transitionTo(OrderStatus::PROCESSING);
    expect($order->status)->toBe(OrderStatus::PROCESSING);

    // Invalid transition
    expect(fn() => $order->transitionTo(OrderStatus::PENDING))
        ->toThrow(InvalidStateTransition::class);
});

test('cache keys are consistent', function () {
    $userId = 123;

    $key1 = CacheService::getUserKey($userId);
    $key2 = sprintf(CacheService::USER_KEY, $userId);

    expect($key1)->toBe($key2)
        ->and($key1)->toBe('user:123');
});

test('validation rules are applied correctly', function () {
    $data = ['username' => 'ab']; // Too short

    $validator = Validator::make($data, [
        'username' => ValidationRules::username()
    ]);

    expect($validator->fails())->toBeTrue();
});

Best Practices

最佳实践

  1. Group related constants
    php
    class OrderConstants
{
    // Statuses
    public const STATUS_PENDING = 'pending';
    public const STATUS_PAID = 'paid';

    // Limits
    public const MAX_ITEMS = 100;
    public const MIN_TOTAL = 10.00;
}
  2. Use descriptive names
    php
    // BAD
const TIMEOUT = 30;

// GOOD
const API_TIMEOUT_SECONDS = 30;
  3. Document units and meanings
    php
    class RateLimits
{
    /** Maximum requests per minute for anonymous users */
    public const ANONYMOUS_PER_MINUTE = 20;

    /** Maximum requests per minute for authenticated users */
    public const AUTHENTICATED_PER_MINUTE = 60;

    /** Lockout duration in minutes after max attempts */
    public const LOCKOUT_MINUTES = 15;
}
  4. Validate against constants
    php
    public function setRole(string $role): void
{
    if (!in_array($role, UserRole::ALL)) {
        throw new InvalidArgumentException("Invalid role: {$role}");
    }

    $this->role = $role;
}
  5. Use configuration for environment-specific values
    php
    // Don't use constants for environment-specific values
// BAD: const API_KEY = 'abc123';

// GOOD: Use config
'api_key' => env('EXTERNAL_API_KEY'),
  6. Create helper functions for complex constants
    php
    class DateConstants
{
    public static function secondsIn(string $unit): int
    {
        return match($unit) {
            'minute' => 60,
            'hour' => 3600,
            'day' => 86400,
            'week' => 604800,
            default => throw new InvalidArgumentException("Unknown unit: {$unit}")
        };
    }
}

// Usage
$cacheTime = DateConstants::secondsIn('hour') * 2; // 2 hours
Remember: Constants make your code self-documenting, reduce bugs from typos, and make refactoring much safer!
  1. 对相关常量进行分组
    php
    class OrderConstants
{
    // Statuses
    public const STATUS_PENDING = 'pending';
    public const STATUS_PAID = 'paid';

    // Limits
    public const MAX_ITEMS = 100;
    public const MIN_TOTAL = 10.00;
}
  2. 使用描述性名称
    php
    // BAD
const TIMEOUT = 30;

// GOOD
const API_TIMEOUT_SECONDS = 30;
  3. 说明单位与含义
    php
    class RateLimits
{
    /** Maximum requests per minute for anonymous users */
    public const ANONYMOUS_PER_MINUTE = 20;

    /** Maximum requests per minute for authenticated users */
    public const AUTHENTICATED_PER_MINUTE = 60;

    /** Lockout duration in minutes after max attempts */
    public const LOCKOUT_MINUTES = 15;
}
  4. 针对常量进行验证
    php
    public function setRole(string $role): void
{
    if (!in_array($role, UserRole::ALL)) {
        throw new InvalidArgumentException("Invalid role: {$role}");
    }

    $this->role = $role;
}
  5. 针对环境特定值使用配置
    php
    // Don't use constants for environment-specific values
// BAD: const API_KEY = 'abc123';

// GOOD: Use config
'api_key' => env('EXTERNAL_API_KEY'),
  6. 为复杂常量创建辅助函数
    php
    class DateConstants
{
    public static function secondsIn(string $unit): int
    {
        return match($unit) {
            'minute' => 60,
            'hour' => 3600,
            'day' => 86400,
            'week' => 604800,
            default => throw new InvalidArgumentException("Unknown unit: {$unit}")
        };
    }
}

// Usage
$cacheTime = DateConstants::secondsIn('hour') * 2; // 2 hours
记住：常量让你的代码自文档化，减少打字错误导致的bug，让重构更加安全！