configloader.php

<?php

namespace Game\Config;

use Symfony\Component\Config\Loader\FileLoader;
use Symfony\Component\Yaml\Yaml;

class ConfigLoader extends FileLoader
{

    /**
     * Loads a resource.
     *
     * @param mixed $file The resource
     * @param string $type The resource type
     */
    public function load($file, $type = null)
    {
        $configValues = Yaml::parse($file);

        if (isset($configValues['imports']) ) {
            $test = $this->import($_SERVER["DOCUMENT_ROOT"] . '/../src/Test/Resources/config/' . $configValues['imports'][0]['resource']);
            unset($configValues['imports']);
            $configValues += $test;
        }
        return $configValues;
    }

    /**
     * Returns true if this class supports the given resource.
     *
     * @param mixed $resource A resource
     * @param string $type The resource type
     *
     * @return bool    true if this class supports the given resource, false otherwise
     */
    public function supports($resource, $type = null)
    {
        return is_string($resource) && 'yml' === pathinfo(
            $resource,
            PATHINFO_EXTENSION
        );
    }
}

index.php

$configDirectories = $_SERVER["DOCUMENT_ROOT"] . '/../src/Test/Resources/config';
$locator = new FileLocator($configDirectories);

$loaderResolver = new LoaderResolver(array(new ConfigLoader($locator)));
$delegatingLoader = new DelegatingLoader($loaderResolver);

$configPreProcess = $delegatingLoader->load($configDirectories . '/config_' . $environment . '.yml');
var_dump($configPreProcess);

$processor = new Processor();
$configuration = new GlobalConfiguration;
$config = $processor->processConfiguration(
    $configuration,
    $configPreProcess)
;