php - How to regularly match the domain name in the middle of the URL

Question

https://so.m.sm.cn/
https://m.sm.cn/
https://www.google.com/
https://m.sogou.com/
https://wap.sogou.com/
https://m.baidu.com/
https://www.google.fr/
https://wisd.sogou.com/

How to write the regular expression? I only want to extract the middle of these domain names, such as: baidu, sm, google, sogou

I can write https://m.sm.cn/ alone, but I can’t write https://so.m.sm.cn/ if I add this.
Help! ! !

Answer 1

php doesn’t work, this is for python, this is just a reference. In other cases, think more on your own.

import re

pattern=re.compile(r'\.([^\.]*?)\.[^\.]*?$')
a=re.findall(pattern,'www.ab.baidu.com')
print a 
#输出['baidu']

Answer 2

preg_match('#://([\w\-\.]+)/?\b#',$string,$m) && $domain=$m[1];