How does PHP get the code instance of the region where the IP belongs (pure code)

$ip=get_client_ip();if(!preg_match("/^[\d]+\.[\d]+\.[\d]+\.[\d]+$/isU",$ip)){    
echo "IP地址错误";
}else{    
//淘宝IP接口
    $url='http://ip.taobao.com/service/getIpInfo.php?ip='.$ip;  
    $result = file_get_contents($url);  
    $result = json_decode($result,true);  
    if($result['code']!==0 || !is_array($result['data'])){        
    echo "IP地址错误";
    }else{
        print_r($result);
    }
}/**
 * 获取客户端IP地址
 * @param integer $type 返回类型 0 返回IP地址 1 返回IPV4地址数字
 * @param boolean $adv 是否进行高级模式获取（有可能被伪装） 
 * @return mixed
 */function get_client_ip($type = 0,$adv=true) {
    $type       =  $type ? 1 : 0;    static $ip  =   NULL;    
    if ($ip !== NULL) return $ip[$type];    
    if($adv){        
    if (isset($_SERVER['HTTP_X_FORWARDED_FOR'])) {            
    $arr    =   explode(',', $_SERVER['HTTP_X_FORWARDED_FOR']);            
    $pos    =   array_search('unknown',$arr);            
    if(false !== $pos) unset($arr[$pos]);            
    $ip     =   trim($arr[0]);
        }elseif (isset($_SERVER['HTTP_CLIENT_IP'])) {            
        $ip     =   $_SERVER['HTTP_CLIENT_IP'];
        }elseif (isset($_SERVER['REMOTE_ADDR']))
         {            
        $ip     =   $_SERVER['REMOTE_ADDR'];
        }
    }elseif (isset($_SERVER['REMOTE_ADDR'])) {        
    $ip     =   $_SERVER['REMOTE_ADDR'];
    }    
    // IP地址合法验证
    $long = sprintf("%u",ip2long($ip));    
    $ip   = $long ? array($ip, $long) : array('0.0.0.0', 0);    
    return $ip[$type];
}