public static function camelize($string, $separator = '_') : string
    {
        if(is_array($separator))
        {
            $separator = "(\\" . implode("|\\", $separator) . ")";
        }
        else
        {
            $separator = '\\' . $separator;
        }
        return preg_replace_callback(
            "/{$separator}[a-zA-Z]/", 
            function ($matches) 
            {
                return strtoupper($matches[0][1]);
            }, 
            strtolower($string)
        );
    }