index.php

<?php

// map class, map method, data
$postMapper = new Mapper('post', 'y', ['x' => 'y']);
$mappedData = $m->map();

Mapper.php

<?php

class Mapper
{
    private $instance;
    
    function __construct (string $type, string $method, array $data)
    {
        if ($type == 'post')
        {
            $this->instance = $this->postMapper($method, $data);
        }
    }
    
    private function postMapper (string $method, array $data)
    {
        return new PostMapper($method, $data);
    }
    
    public function map ()
    {
        return $instance;
    }
    
}

PostMapper.php

<?php

class PostMapper
{
    private $method;
    private $data;
    
    function __construct ($method, $data)
    {
        $this->method = $method;
        $this->data = $data;
    }
    
    private function decide()
    {
        if ($this->method == 'x')
        {
            $this->mapX();
        }
        else if ($this->method == 'y')
        {
            $this->mapY();
        }
    }
    
    private function mapX ()
    {
        // map some data on one way
    }
    
    private function mapY ()
    {
        // map some data on another way
    }
}