explanation of service container

index.php

<?php

class Battery {

    /**
     * Battery constructor.
     * @param int $procent
     */
    public function __construct(int $procent)
    {
        $this->procent = $procent;
    }
}

class Calc {

    /**
     * Calc constructor.
     */
    public function __construct(Battery $battery)
    {
        $this->battery = $battery;
    }
}

class Lamp {

    /**
     * Lamp constructor.
     */
    public function __construct(Battery $battery)
    {
        $this->battery = $battery;
    }
}

class Container {
    protected $services = [
//        Battery::class => function(){}
    ];

    public function get(string $alias){
        return $this->services[$alias]();
    }

    public function set(string $alias, callable $factory){
        $this->services[$alias] = $factory;
    }
}


$container = new Container();

$container->set(Battery::class, function(){
    return new Battery(12);
});

$container->set(Calc::class, function() use ($container){
    $battery = $container->get(Battery::class);

    return new Calc($battery);
});
$container->set(Lamp::class, function() use ($container){
    $battery = $container->get(Battery::class);
    
    return new Lamp($battery);
});

$calc = $container->get(Calc::class);