ioc2.php

<?php 

class Container
{
    public function make($className){}
    
    public function register($className, $callback){}
}

// initialize the container and register some classes
$c = new Container();
$c->register(FacebookSDK::class,function(){
    return new FacebookSDK([
        "app_key" => env('FB_APP_KEY'),
        "app_secret" => env('FB_APP_SECRET')
    ]);
});

// let the container return some registered classes (e.g. within the controller)
$fb = $c->make(FacebookSDK::class);