Minimal DI container

Container.php

<?php

class Container
{
    /** @var Closure[] */
    private $factories = [];

    /** @var array */
    private $components = [];

    public function get($id)
    {
        if (!isset($this->components[$id])) {
            $this->components[$id] = call_user_func($this->factories[$id], $this);
        }

        return $this->components[$id];
    }

    public function set($id, $value)
    {
        $this->components[$id] = $value;
    }

    public function register($id, Closure $func)
    {
        $this->factories[$id] = $func;
    }
}