PHP：静态函数没有返回正确的值

Question

我有获取IP地址的功能，如果我手动将该功能放在我的PHP页面下工作。但是我想把它作为静态函数放在一个类中，而不是给它返回值::1

audit.class

public static function get_client_ip() {
        $ipaddress = '';
        if (getenv('HTTP_CLIENT_IP'))
            $ipaddress = getenv('HTTP_CLIENT_IP');
        else if(getenv('HTTP_X_FORWARDED_FOR'))
            $ipaddress = getenv('HTTP_X_FORWARDED_FOR');
        else if(getenv('HTTP_X_FORWARDED'))
            $ipaddress = getenv('HTTP_X_FORWARDED');
        else if(getenv('HTTP_FORWARDED_FOR'))
            $ipaddress = getenv('HTTP_FORWARDED_FOR');
        else if(getenv('HTTP_FORWARDED'))
           $ipaddress = getenv('HTTP_FORWARDED');
        else if(getenv('REMOTE_ADDR'))
            $ipaddress = getenv('REMOTE_ADDR');
        else
            $ipaddress = 'UNKNOWN';
        return $ipaddress;
    }

.PHP

echo Audit::get_client_ip();
//result is ::1
//instead of ip******