====

Use a custom Eloquent “Castable” class (i.e. a Value Object) for your model attributes so you get strong typing, encapsulated logic and automatic DB conversion. 

1. Create your Value Object implementing the Castable & CastsAttributes contracts:  
   ```php
   use Illuminate\Contracts\Database\Eloquent\Castable;
   use Illuminate\Contracts\Database\Eloquent\CastsAttributes;

   class Money implements Castable, CastsAttributes
   {
       public int $amount;
       public string $currency;

       public function __construct(int $amount, string $currency = 'USD')
       {
           $this->amount   = $amount;
           $this->currency = $currency;
       }

       // Eloquent will call this when retrieving
       public function get($model, string $key, $value, array $attributes)
       {
           [$amount, $currency] = explode(':', $value);
           return new self((int)$amount, $currency);
       }

       // Eloquent will call this when saving
       public function set($model, string $key, $value, array $attributes)
       {
           /** @var Money $value */
           return "{$value->amount}:{$value->currency}";
       }

       // required by Castable
       public static function castUsing(array $arguments)
       {
           return new self(...$arguments);
       }
   }
   ```

2. Register it in your model’s `$casts`:  
   ```php
   class Product extends Model
   {
       protected $casts = [
           'price' => Money::class.':USD',  // optional constructor args
       ];
   }
   ```

Now `$product->price` is a `Money` object with your domain logic, and Eloquent handles serialization to/from the database automatically.