gistfile1.php

<?php

class TransformerAbstract
{
    private $fields;
    private $allowedFields = array('id', 'name', 'phone', 'email', 'bio', 'num_friends');
    private $partialFields = array(
        'id' => array('id', 'name'),
        'info' => array('name', 'phone', 'email', 'bio'),
        'bio' => array('bio')
    );
    private $partials;
    private $defaultPartials = array('id');
    
    public function setPartials(array $partials)
    {
        $this->partials = $partials;
    }
    
    public function transform($object)
    {
        $data = // do normal transform
        
        // Extract only the requested fields, do this before embedding. This is somewhat wasteful but simplifies the code since we just use string keys for fields
        if ($this->partials) {
            $killKeys = array_diff(
                array_keys($data),
                $this->getFieldsForPartials($this->partials)
            );
            foreach ($killKey as $killKeys) {
                unset($data[$killKey]);
            }
        }
        
        // Do embedding
        
        return $data;
    }

    protected function getFieldsForPartials(array $partials)
    {
        $partialFields = $this->partialFields;
        
        return array_reduce(
            $partials,
            function ($carry, $partial) use ($partialFields) {
                return array_merge($carry, $partialFields[$partial]);
            },
            array()
        );
    }
}