transformer.php

<?php namespace Bardell\Transformers;

abstract class Transformer {

	public function transformCollection(array $items) {
		return array_map([$this, 'transform'], $items);
	}

	public abstract function transform($item); 

}

WordCardTransformer.php

<?php namespace Bardell\Transformers;

class WordCardTransformer extends Transformer {

	public function transform($wordcard) {
		return [
			'word' => $wordcard['word'],
			'answer' => $wordcard['answer'],
			'id' => $wordcard['id']
		];
	}

}