dependency-inversion-principle-example1.php

<?php
namespace Acme\Services;
 
class Container {
    private $services = array();
 
    public function set($name, $instance)
    {
        $this->services[$name] = $instance;
    }
    
    public function get($name)
    {
        return $this->services[$name];
    }
}
 
interface MapperInterface
{
    public function findAll($table);
}
 
interface FinderInterface
{
    public function findAll();
}
 
interface ListerInterface
{
    public function list();
}
 
class SomeDatabaseMapper implements MapperInterface
{
    public function findAll($table)
    {
        //Find all entries in some way
    }
}
 
class MovieFinder implements FinderInterface
{
    private $db;
 
    public function __construct(MapperInterface $db) {
        $this->db = $db;
    }
 
    public function findAll()
    {
        return $this->db->findAll("movies");
    }
}
 
class MovieLister implements ListerInterface
{
    private $movieFinder;
 
    public function __construct(FinderInterface $movieFinder) {
        $this->movieFinder = $movieFinder;
    }
 
    public function list()
    {   
        return $this->movieFinder->findAll();
    }
}
 
$container = new Container();
$container->set("db", new SomeDatabaseMapper());
$container->set("movie_finder", new MovieFinder($container->get("db")));
$container->set("movie_lister", new MovieLister($container->get("movie_finder")));
 
$movieList = $container->get("movie_lister")->list();