public static function constant($name)
    {
        $name      = strtoupper($name);
        $value     = null;
        $constants = self::constants();
        if (isset($constants[$name])) {
            $value = $constants[$name];
        } else {
            throw new \Headzoo\Core\Exceptions\UndefinedConstantException(
                "Undefined constant {$name}."
            );
        }
        
        return $value;
    }