Use enums instead of magic strings

How to do it

Define the set once, and use it in signatures, database mapping and tests. The type checker then catches typos and missing cases. At an API boundary, also follow use enums for fixed values, so clients survive values added later.

Example

// Bad: a typo compiles and fails quietly
if ($order->status === 'payed') { /* ... */ }

// Good: the set of values is a type
enum OrderStatus: string { case Pending = 'pending'; case Paid = 'paid'; case Refunded = 'refunded'; }
if ($order->status === OrderStatus::Paid) { /* ... */ }

from enum import StrEnum

class OrderStatus(StrEnum):
    PENDING = "pending"
    PAID = "paid"
    REFUNDED = "refunded"

if order.status is OrderStatus.PAID: ...

How to check

The tools flag unhandled cases. Examples are typescript-eslint switch-exhaustiveness-check and PHPStan's check that a match covers every enum case. Reviewers fail comparisons of status fields with string literals.