> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/spatie/laravel-data/llms.txt
> Use this file to discover all available pages before exploring further.

# Creating a Transformer

> Build custom transformers to convert complex values into simple types

Transformers take complex values and transform them into simple types. For example, a `Carbon` object could be transformed to `16-05-1994T00:00:00+00`.

## Transformer Interface

Implement the `Transformer` interface:

```php theme={null}
interface Transformer
{
    public function transform(DataProperty $property, mixed $value, TransformationContext $context): mixed;
}
```

### Parameters

* **property** - `DataProperty` object representing the property being transformed ([read more](/advanced-usage/internal-structures))
* **value** - The value to transform (never `null`)
* **context** - `TransformationContext` containing:
  * `transformValues` - Whether values should be transformed
  * `mapPropertyNames` - Whether property names should be mapped
  * `wrapExecutionType` - The execution type for wrapping values
  * `transformers` - Collection of available transformers

### Return Value

Return the transformed value.

## Example Transformer

```php theme={null}
use Spatie\LaravelData\Transformers\Transformer;
use Spatie\LaravelData\Support\DataProperty;
use Spatie\LaravelData\Support\Transformation\TransformationContext;

class DateTimeTransformer implements Transformer
{
    public function transform(DataProperty $property, mixed $value, TransformationContext $context): string
    {
        return $value->format('Y-m-d H:i:s');
    }
}
```

Use in your data class:

```php theme={null}
use Spatie\LaravelData\Attributes\WithTransformer;

class SongData extends Data
{
    public function __construct(
        public string $title,
        #[WithTransformer(DateTimeTransformer::class)]
        public DateTime $releasedAt,
    ) {
    }
}
```

## Combining Transformers and Casts

Create a class that both transforms and casts:

```php theme={null}
class ToUpperCastAndTransformer implements Cast, Transformer
{
    public function cast(DataProperty $property, mixed $value, array $properties, CreationContext $context): string
    {
        return strtoupper($value);
    }
    
    public function transform(DataProperty $property, mixed $value, TransformationContext $context): string
    {
        return strtoupper($value);
    }
}
```

Use with the `WithCastAndTransformer` attribute:

```php theme={null}
class SongData extends Data
{
    public function __construct(
        public string $title,
        #[WithCastAndTransformer(ToUpperCastAndTransformer::class)]
        public string $artist,
    ) {
    }
}
```