Symfony\Component\DependencyInjection\Loader\YamlFileLoader::resolveServices PHP Method

    private function resolveServices($value)
    {
        if (is_array($value)) {
            $value = array_map(array($this, 'resolveServices'), $value);
        } elseif (is_string($value) && 0 === strpos($value, '@=')) {
            return new Expression(substr($value, 2));
        } elseif (is_string($value) && 0 === strpos($value, '@')) {
            if (0 === strpos($value, '@@')) {
                $value = substr($value, 1);
                $invalidBehavior = null;
            } elseif (0 === strpos($value, '@?')) {
                $value = substr($value, 2);
                $invalidBehavior = ContainerInterface::IGNORE_ON_INVALID_REFERENCE;
            } else {
                $value = substr($value, 1);
                $invalidBehavior = ContainerInterface::EXCEPTION_ON_INVALID_REFERENCE;
            }

            if ('=' === substr($value, -1)) {
                $value = substr($value, 0, -1);
                $strict = false;
            } else {
                $strict = true;
            }

            if (null !== $invalidBehavior) {
                $value = new Reference($value, $invalidBehavior, $strict);
            }
        }

        return $value;
    }