MyParameterBag.php

<?php
use Symfony\Component\DependencyInjection\ParameterBag\ParameterBagInterface;

// Interface implementation for testing purposes
class MyParameterBag implements ParameterBagInterface
{
    private $container = array();

    public function add(array $parameters)
    {
        echo '-- Bag::add ', print_r($parameters, true), ' --', PHP_EOL;
    }

    public function all()
    {
        echo '-- Bag::all --', PHP_EOL;
        return $this->container;
    }
    
    public function clear()
    {
        echo '-- Bag::clear --', PHP_EOL;
        $this->container = array();
    }
    
    public function get($name)
    {
        echo '-- Bag::get ', print_r(compact('name'), true), ' --', PHP_EOL;
        return isset($this->container[$name]) ? $this->container[$name] : null;
    }
    
    public function has($name)
    {
        echo '-- Bag::has ', print_r(compact('name'), true), ' --', PHP_EOL;
        return isset($this->container[$name]);
    }

    public function set($name, $value)
    {
        echo '-- Bag::set ', print_r(compact('name', 'value'), true), ' --', PHP_EOL;
        $this->container[$name] = $value;
    }
}

test.php

<?php
use Symfony\Component\DependencyInjection\ContainerBuilder,
    Symfony\Component\DependencyInjection\Loader\XmlFileLoader,
    Symfony\Component\Config\FileLocator;

$bag       = new MyParameterBag();
$container = new ContainerBuilder($bag);
$path      = explode(PATH_SEPARATOR, get_include_path());
$locator   = new FileLocator($path);
$loader    = new XmlFileLoader($container, $locator);
$loader->load('dependencies.xml');

/**
 * Throws:
 * Fatal error: Call to undefined method MyParameterBag::resolveValue()
 *    in Symfony/Component/DependencyInjection/ContainerBuilder.php on line 725
 */
$container->get('entityManager');