How to hide the last two digits of the IP address in php and replace the middle digits of the mobile phone number with *

<?php
/**
  * 隐藏IP后两位
  * by 程序员之家 http://bbs.it-home.org
*/
function ip2unkonw($ip)
{
    $add = explode('.', $ip, 4);
    return $add[0]. '.'. $add[1]. '.*.*';
}
?>

<?php
//隐藏后一位
return preg_replace('/(\d+)\.(\d+)\.(\d+)\.(\d+)/is',"$1.$2.$3.*",$ip); 

//隐藏IP最后几位为*
echo ereg_replace("[^\.]{1,3}$","*",$ip);
?>

<?php
//隐藏手机号部分数字
$string = "13811111100";
$pattern = "/(1\d{1,2})\d\d(\d{0,3})/";
$replacement = "\$1****\$3";

print preg_replace($pattern, $replacement, $string);
?>

<?
//--隐藏IP后几位
//by 程序员之家 bbs.it-home.org
$ip='127.0.0.1';
$reg1='/((?:\d+\.){3})\d+/';
$reg2='~(\d+)\.(\d+)\.(\d+)\.(\d+)~';
echo preg_replace($reg1,"\\1*",$ip);//以上输出结果为：127.0.0.*
echo "------------------<br/>";
echo preg_replace($reg2,"$1.$2.*.*",$ip);//以上输出结果为：127.0.*.*
?>