core/Request.php
public static function getCookie(string $name, $def = null)
    {
        return isset($_COOKIE[$name]) ? $_COOKIE[$name] : $def;
    }
public static function getCookie(string $name, $def = null)
    {
        return isset($_COOKIE[$name]) ? $_COOKIE[$name] : $def;
    }
获取cookie
@param string $name
@param null $def
@return null