PHP实现获取url地址中顶级域名的方法示例

<?php
/
  @Author: Ding Jianlong
  @Date:  2019-03-07 16:14:04
  @Last Modified by:  Ding Jianlong
  @Last Modified time: 2019-03-20 13:45:12
 /
header('content-type:text/html;charset=utf-8');
//获取顶级域名
function getTopHost($url){
 $url = strtolower($url);  //转成小写
 $hosts = parse_url($url);
 $host = $hosts['host'];
 //查看是几级域名
  $data = explode('.', $host);
  $n = count($data);
  //判断是否是双后缀
  $preg = '/[\w].+\.(|||gov|edu)\.$/';
  if(($n > 2) && preg_match($preg,$host)){
   //双后缀取后3位
   $host = $data[$n-3].'.'.$data[$n-2].'.'.$data[$n-1];
  }else{
   //非双后缀取后两位
   $host = $data[$n-2].'.'.$data[$n-1];
  }
  return $host;
}
// 测试
echo getTopHost("http://ABC./s/j?wd=djl"),'<br>';
echo getTopHost("http://.abc./s/j?wd=djl"),'<br>';
echo getTopHost("http://2..abc./s/j?wd=djl"),'<br>';
echo getTopHost("https://mp.weixin.qq./s?__=MzA3ODI3ODUzMw=="),'<br>';
echo getTopHost("http://cfi../"),'<br>';
echo getTopHost("http://.cfi.NEt./"),'<br>';
echo getTopHost("https://.sina../?from=kandian"),'<br>';