Simple Service Container Example

ServiceContainer.php

<?php

class ServiceContainer
{
    protected $services = [];

    protected function setCallable($serviceKey, Callable $service)
    {
        $this->services[$serviceKey] = $service;
        return $this;
    }

    protected function setInstance($serviceKey, $instance)
    {
        $this->services[$serviceKey] = function() use($instance)
        {
            return $instance;
        });
        return $this;
    }

    public function set($serviceKey, $service)
    {
        if($service instanceof Callable) {
            return $this->setCallable($serviceKey, $service)
        } elseif(is_object($service) {
            return $this->setInstance($serviceKey, $service);
        }
        throw InvalidArgumentException('Services must be either an object instance or Callable, found [' . gettype($service) . '] instead.' );
    }

    public function get($serviceKey)
    {
        if( empty($this->services[$serviceKey]) ) {
            throw new InvalidArgumentException("Cannot locate a service with the key [$serviceKey]");
        }
        return $this->services[$serviceKey]($this);
    }
}