Symfony Config Loader

<?php
namespace MyCompany\Api\DependencyInjection;

use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Loader;
use Symfony\Component\Config\FileLocator;
use MyCompany\Api\Exception\ApiException;

/**
 * Class MyCompanyApiConfig
 * @package MyCompany\Api\DependencyInjection
 */
class MyCompanyApiConfig {
  /** @var MyCompanyApiConfig - Hold an instance of the class */
  private static $instance;
  private static $container;

  /**
   * The singleton method
   *
   * @return \MyCompany\Api\DependencyInjection\MyCompanyApiConfig
   */
  public static function getInstance() {
    if (!isset(self::$instance)) {
      self::$instance = new MyCompanyApiConfig();
    }

    return self::$instance;
  }

  /**
   * Handle dynamic, static calls to the object.
   *
   * @param  string  $method
   * @param  array   $args
   * @return mixed
   *
   * @throws ApiException
   */
  public static function __callStatic($method, $args) {
    $instance = static::getInstance();

    if (!$instance) {
      throw new ApiException('Unable to load the class instance.');
    }

    return $instance->$method(...$args);
  }

  /**
   * @param $varName
   * @return mixed
   * @throw \Symfony\Component\DependencyInjection\Exception\InvalidArgumentException
   */
  public static function get($varName) {
    return self::loadConfig()->getParameter($varName);
  }

  /**
   * @return \Symfony\Component\DependencyInjection\ContainerBuilder
   */
  public static function loadConfig() {
    if (empty(self::$container)) {
      self::$container = new ContainerBuilder();

      $loader = new Loader\YamlFileLoader(self::$container, new FileLocator(__DIR__.'/../Resources/config'));
      $loader->load('services.yml');
      $loader->load('config.yml');
    }

    return self::$container;
  }
}